Network Working Group J. Reschke, Ed. Internet-Draft greenbytes Intended status: Standards Track S. Reddy Expires: January 8, 2009 Mitrix J. Davis A. Babich IBM July 7, 2008 Web Distributed Authoring and Versioning (WebDAV) SEARCH draft-reschke-webdav-search-16 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on January 8, 2009. Abstract This document specifies a set of methods, headers, properties and content-types composing WebDAV SEARCH, an application of the HTTP/1.1 protocol to efficiently search for DAV resources based upon a set of client-supplied criteria. Reschke, et al. Expires January 8, 2009 [Page 1]
Internet-Draft WebDAV SEARCH July 2008 Editorial Note (To be removed by RFC Editor before publication) Please send comments to the Distributed Authoring and Versioning (WebDAV) DASL mailing list at <mailto:www-webdav-dasl@w3.org>, which may be joined by sending a message with subject "subscribe" to <mailto:www-webdav-dasl-request@w3.org>. Discussions of the WebDAV DASL mailing list are archived at <http://lists.w3.org/Archives/Public/www-webdav-dasl/>. An issues list and XML and HTML versions of this draft are available from <http://greenbytes.de/tech/webdav/#draft-reschke-webdav-search>. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.1. DASL . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2. Relationship to DAV . . . . . . . . . . . . . . . . . . . 6 1.3. Terms . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.4. Notational Conventions . . . . . . . . . . . . . . . . . . 8 1.5. Note on Usage of 'DAV:' XML Namespace . . . . . . . . . . 9 1.6. An Overview of DASL at Work . . . . . . . . . . . . . . . 9 2. The SEARCH Method . . . . . . . . . . . . . . . . . . . . . . 9 2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2. The Request . . . . . . . . . . . . . . . . . . . . . . . 9 2.2.1. The Request-URI . . . . . . . . . . . . . . . . . . . 10 2.2.2. The Request Body . . . . . . . . . . . . . . . . . . . 10 2.3. The Successful 207 (Multistatus) Response . . . . . . . . 11 2.3.1. Result Set Truncation . . . . . . . . . . . . . . . . 11 2.3.2. Extending the PROPFIND Response . . . . . . . . . . . 12 2.3.3. Example: A Simple Request and Response . . . . . . . . 12 2.3.4. Example: Result Set Truncation . . . . . . . . . . . . 13 2.4. Unsuccessful Responses . . . . . . . . . . . . . . . . . . 14 2.4.1. Example of an Invalid Scope . . . . . . . . . . . . . 14 3. Discovery of Supported Query Grammars . . . . . . . . . . . . 15 3.1. The OPTIONS Method . . . . . . . . . . . . . . . . . . . . 15 3.2. The DASL Response Header . . . . . . . . . . . . . . . . . 16 3.3. DAV:supported-query-grammar-set (protected) . . . . . . . 16 3.4. Example: Grammar Discovery . . . . . . . . . . . . . . . . 16 4. Query Schema Discovery: QSD . . . . . . . . . . . . . . . . . 19 4.1. Additional SEARCH Semantics . . . . . . . . . . . . . . . 19 4.1.1. Example of Query Schema Discovery . . . . . . . . . . 20 5. The DAV:basicsearch Grammar . . . . . . . . . . . . . . . . . 21 5.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 21 5.2. The DAV:basicsearch DTD . . . . . . . . . . . . . . . . . 22 5.2.1. Example Query . . . . . . . . . . . . . . . . . . . . 24 5.3. DAV:select . . . . . . . . . . . . . . . . . . . . . . . . 25 5.4. DAV:from . . . . . . . . . . . . . . . . . . . . . . . . . 25 Reschke, et al. Expires January 8, 2009 [Page 2]
Internet-Draft WebDAV SEARCH July 2008 5.4.1. Relationship to the Request-URI . . . . . . . . . . . 25 5.4.2. Scope . . . . . . . . . . . . . . . . . . . . . . . . 26 5.5. DAV:where . . . . . . . . . . . . . . . . . . . . . . . . 26 5.5.1. Use of Three-Valued Logic in Queries . . . . . . . . . 26 5.5.2. Handling Optional Operators . . . . . . . . . . . . . 26 5.5.3. Treatment of NULL Values . . . . . . . . . . . . . . . 26 5.5.4. Treatment of Properties with mixed/element Content . . 27 5.5.5. Example: Testing for Equality . . . . . . . . . . . . 27 5.5.6. Example: Relative Comparisons . . . . . . . . . . . . 27 5.6. DAV:orderby . . . . . . . . . . . . . . . . . . . . . . . 28 5.6.1. Example of Sorting . . . . . . . . . . . . . . . . . . 28 5.7. Boolean Operators: DAV:and, DAV:or, and DAV:not . . . . . 28 5.8. DAV:eq . . . . . . . . . . . . . . . . . . . . . . . . . . 29 5.9. DAV:lt, DAV:lte, DAV:gt, DAV:gte . . . . . . . . . . . . . 29 5.10. DAV:literal . . . . . . . . . . . . . . . . . . . . . . . 29 5.11. DAV:typed-literal (optional) . . . . . . . . . . . . . . . 29 5.11.1. Example for Typed Numerical Comparison . . . . . . . . 30 5.12. Support for Matching xml:lang Attributes on Properties . . 30 5.12.1. DAV:language-defined (optional) . . . . . . . . . . . 31 5.12.2. DAV:language-matches (optional) . . . . . . . . . . . 31 5.12.3. Example of Language-Aware Matching . . . . . . . . . . 31 5.13. DAV:is-collection . . . . . . . . . . . . . . . . . . . . 31 5.13.1. Example of DAV:is-collection . . . . . . . . . . . . . 32 5.14. DAV:is-defined . . . . . . . . . . . . . . . . . . . . . . 32 5.15. DAV:like . . . . . . . . . . . . . . . . . . . . . . . . . 32 5.15.1. Syntax for the Literal Pattern . . . . . . . . . . . . 33 5.15.2. Example of DAV:like . . . . . . . . . . . . . . . . . 33 5.16. DAV:contains . . . . . . . . . . . . . . . . . . . . . . . 33 5.16.1. Result Scoring (DAV:score Element) . . . . . . . . . . 34 5.16.2. Ordering by Score . . . . . . . . . . . . . . . . . . 35 5.16.3. Examples . . . . . . . . . . . . . . . . . . . . . . . 35 5.17. Limiting the Result Set . . . . . . . . . . . . . . . . . 35 5.17.1. Relationship to Result Ordering . . . . . . . . . . . 35 5.18. The 'caseless' XML Attribute . . . . . . . . . . . . . . . 36 5.19. Query Schema for DAV:basicsearch . . . . . . . . . . . . . 36 5.19.1. DTD for DAV:basicsearch QSD . . . . . . . . . . . . . 36 5.19.2. DAV:propdesc Element . . . . . . . . . . . . . . . . . 37 5.19.3. The DAV:datatype Property Description . . . . . . . . 37 5.19.4. The DAV:searchable Property Description . . . . . . . 38 5.19.5. The DAV:selectable Property Description . . . . . . . 38 5.19.6. The DAV:sortable Property Description . . . . . . . . 38 5.19.7. The DAV:caseless Property Description . . . . . . . . 38 5.19.8. The DAV:operators XML Element . . . . . . . . . . . . 38 5.19.9. Example of Query Schema for DAV:basicsearch . . . . . 40 6. Internationalization Considerations . . . . . . . . . . . . . 40 7. Security Considerations . . . . . . . . . . . . . . . . . . . 41 7.1. Implications of XML External Entities . . . . . . . . . . 41 8. Scalability . . . . . . . . . . . . . . . . . . . . . . . . . 42 Reschke, et al. Expires January 8, 2009 [Page 3]
Internet-Draft WebDAV SEARCH July 2008 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42 9.1. HTTP Headers . . . . . . . . . . . . . . . . . . . . . . . 42 9.1.1. DASL . . . . . . . . . . . . . . . . . . . . . . . . . 42 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 42 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 43 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 43 12.1. Normative References . . . . . . . . . . . . . . . . . . . 43 12.2. Informative References . . . . . . . . . . . . . . . . . . 44 Appendix A. Three-Valued Logic in DAV:basicsearch . . . . . . . . 45 Appendix B. Candidates for Future Protocol Extensions . . . . . . 46 B.1. Collation Support . . . . . . . . . . . . . . . . . . . . 46 B.2. Count . . . . . . . . . . . . . . . . . . . . . . . . . . 47 B.3. Diagnostics for Unsupported Queries . . . . . . . . . . . 47 B.4. Language Matching . . . . . . . . . . . . . . . . . . . . 47 B.5. Matching Media Types . . . . . . . . . . . . . . . . . . . 47 B.6. Query by Name . . . . . . . . . . . . . . . . . . . . . . 48 B.7. Result Paging . . . . . . . . . . . . . . . . . . . . . . 48 B.8. Search Scope Discovery . . . . . . . . . . . . . . . . . . 48 Appendix C. Change Log (to be removed by RFC Editor before publication) . . . . . . . . . . . . . . . . . . . . 48 C.1. From draft-davis-dasl-protocol-xxx . . . . . . . . . . . . 48 C.2. since start of draft-reschke-webdav-search . . . . . . . . 50 C.3. since draft-reschke-webdav-search-00 . . . . . . . . . . . 52 C.4. since draft-reschke-webdav-search-01 . . . . . . . . . . . 52 C.5. since draft-reschke-webdav-search-02 . . . . . . . . . . . 52 C.6. since draft-reschke-webdav-search-03 . . . . . . . . . . . 53 C.7. since draft-reschke-webdav-search-04 . . . . . . . . . . . 53 C.8. since draft-reschke-webdav-search-05 . . . . . . . . . . . 54 C.9. since draft-reschke-webdav-search-06 . . . . . . . . . . . 54 C.10. since draft-reschke-webdav-search-07 . . . . . . . . . . . 55 C.11. since draft-reschke-webdav-search-08 . . . . . . . . . . . 55 C.12. since draft-reschke-webdav-search-09 . . . . . . . . . . . 55 C.13. since draft-reschke-webdav-search-10 . . . . . . . . . . . 56 C.14. since draft-reschke-webdav-search-11 . . . . . . . . . . . 56 C.15. since draft-reschke-webdav-search-12 . . . . . . . . . . . 56 C.16. since draft-reschke-webdav-search-13 . . . . . . . . . . . 56 C.17. since draft-reschke-webdav-search-14 . . . . . . . . . . . 56 C.18. since draft-reschke-webdav-search-15 . . . . . . . . . . . 57 Appendix D. Resolved issues (to be removed by RFC Editor before publication) . . . . . . . . . . . . . . . . . 57 D.1. standardstrack . . . . . . . . . . . . . . . . . . . . . . 57 D.2. acls . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 D.3. scope-discovery . . . . . . . . . . . . . . . . . . . . . 58 D.4. 3.2-listsyntax . . . . . . . . . . . . . . . . . . . . . . 58 Appendix E. Open issues (to be removed by RFC Editor prior to publication) . . . . . . . . . . . . . . . . . . . . 58 E.1. edit . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 Reschke, et al. Expires January 8, 2009 [Page 4]
Internet-Draft WebDAV SEARCH July 2008 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 60 Intellectual Property and Copyright Statements . . . . . . . . . . 62 Reschke, et al. Expires January 8, 2009 [Page 5]
Internet-Draft WebDAV SEARCH July 2008 1. Introduction 1.1. DASL This document defines Web Distributed Authoring and Versioning (WebDAV) SEARCH, an application of HTTP/1.1 forming a lightweight search protocol to transport queries and result sets that allows clients to make use of server-side search facilities. It is based on the expired internet draft for DAV Searching & Locating [DASL]. [DASLREQ] describes the motivation for DASL. In this specification, the terms "WebDAV SEARCH" and "DASL" are used interchangeably. DASL minimizes the complexity of clients so as to facilitate widespread deployment of applications capable of utilizing the DASL search mechanisms. DASL consists of: o the SEARCH method and the request/response formats defined for it (Section 2), o feature discovery through the "DASL" response header and the optional DAV:supported-grammar-set property (Section 3), o optional grammar schema discovery (Section 4) and o one mandatory grammar: DAV:basicsearch (Section 5). 1.2. Relationship to DAV DASL relies on the resource and property model defined by [RFC4918]. DASL does not alter this model. Instead, DASL allows clients to access DAV-modeled resources through server-side search. 1.3. Terms This document uses the terms defined in [RFC2616], in [RFC4918], in [RFC3253] and in this section. Criteria An expression against which each resource in the search scope is evaluated. Query A query is a combination of a search scope, search criteria, result record definition, sort specification, and a search Reschke, et al. Expires January 8, 2009 [Page 6]
Internet-Draft WebDAV SEARCH July 2008 modifier. Query Grammar A set of definitions of XML elements, attributes, and constraints on their relations and values that defines a set of queries and the intended semantics. Query Schema A listing, for any given grammar and scope, of the properties and operators that may be used in a query with that grammar and scope. Result A result is a result set, optionally augmented with other information describing the search as a whole. Result Record A description of a resource. A result record is a set of properties, and possibly other descriptive information. Result Record Definition A specification of the set of properties to be returned in the result record. Result Set A set of records, one for each resource for which the search criteria evaluated to True. Scope A set of resources to be searched. Search Arbiter A resource that supports the SEARCH method. Search Modifier An instruction that governs the execution of the query but is not part of the search scope, result record definition, the search criteria, or the sort specification. An example of a search modifier is one that controls how much time the server can spend on the query before giving a response. Reschke, et al. Expires January 8, 2009 [Page 7]
Internet-Draft WebDAV SEARCH July 2008 Sort Specification A specification of an ordering on the result records in the result set. 1.4. Notational Conventions This specification uses the Augmented Backus-Naur Form (ABNF) notation of [RFC5234], unless explicitly stated otherwise. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. This document uses XML DTD fragments ([XML], Section 3.2) as a purely notational convention. WebDAV request and response bodies can not be validated by a DTD due to the specific extensibility rules defined in Section 17 of [RFC4918] and due to the fact that all XML elements defined by this specification use the XML namespace name "DAV:". In particular: 1. element names use the "DAV:" namespace, 2. element ordering is irrelevant unless explicitly stated, 3. extension elements (elements not already defined as valid child elements) may be added anywhere, except when explicitly stated otherwise, 4. extension attributes (attributes not already defined as valid for this element) may be added anywhere, except when explicitly stated otherwise. When an XML element type in the "DAV:" namespace is referenced in this document outside of the context of an XML fragment, the string "DAV:" will be prefixed to the element type. Similarly, when an XML element type in the namespace "http://www.w3.org/2001/XMLSchema" is referenced in this document outside of the context of an XML fragment, the string "xs:" will be prefixed to the element type. This document inherits, and sometimes extends, DTD productions from Section 14 of [RFC4918]. Reschke, et al. Expires January 8, 2009 [Page 8]
Internet-Draft WebDAV SEARCH July 2008 1.5. Note on Usage of 'DAV:' XML Namespace This specification defines elements, properties and condition names in the XML namespace "DAV:". In general, only specifications authored by IETF working groups are supposed to do this. In this case an exception was made, because WebDAV SEARCH started its life in the IETF DASL working group (<http://www.webdav.org/dasl/>, and at the time the working group closed down there was already significant deployment of this specification. 1.6. An Overview of DASL at Work One can express the basic usage of DASL in the following steps: o The client constructs a query using the DAV:basicsearch grammar. o The client invokes the SEARCH method on a resource that will perform the search (the search arbiter) and includes a text/xml or application/xml request entity that contains the query. o The search arbiter performs the query. o The search arbiter sends the results of the query back to the client in the response. The server MUST send an entity that matches the WebDAV multistatus format ([RFC4918], Section 13). 2. The SEARCH Method 2.1. Overview The client invokes the SEARCH method to initiate a server-side search. The body of the request defines the query. The server MUST emit an entity matching the WebDAV multistatus format ([RFC4918], Section 13). The SEARCH method plays the role of transport mechanism for the query and the result set. It does not define the semantics of the query. The type of the query defines the semantics. 2.2. The Request The client invokes the SEARCH method on the resource named by the Request-URI. Reschke, et al. Expires January 8, 2009 [Page 9]
Internet-Draft WebDAV SEARCH July 2008 2.2.1. The Request-URI The Request-URI identifies the search arbiter. Any HTTP resource may function as search arbiter. It is not a new type of resource (in the sense of DAV:resourcetype as defined in [RFC4918], Section 15.9), nor does it have to be a WebDAV-compliant resource. The SEARCH method defines no relationship between the arbiter and the scope of the search, rather the particular query grammar used in the query defines the relationship. For example, a query grammar may force the Request-URI to correspond exactly to the search scope. 2.2.2. The Request Body The server MUST process a text/xml or application/xml request body, and MAY process request bodies in other formats. See [RFC3023] for guidance on packaging XML in requests. Marshalling: If a request body with content type text/xml or application/xml is included, it MUST be either a DAV:searchrequest or a DAV:query- schema-discovery XML element. Its single child element identifies the query grammar. For DAV:searchrequest, the definition of search criteria, the result record, and any other details needed to perform the search depend on the individual search grammar. For DAV:query-schema-discovery, the semantics is defined in Section 4. Preconditions: (DAV:search-grammar-discovery-supported): when an XML request body is present and has a DAV:query-schema-discovery document element, the server MUST support the query schema discovery mechanism described in Section 4. (DAV:search-grammar-supported): when an XML request body is present, the search grammar identified by the document element's child element must be a supported search grammar. (DAV:search-multiple-scope-supported): if the SEARCH request specified multiple scopes, the server MUST support this optional feature. Reschke, et al. Expires January 8, 2009 [Page 10]
Internet-Draft WebDAV SEARCH July 2008 (DAV:search-scope-valid): the supplied search scope must be valid. There can be various reasons for a search scope to be invalid, including unsupported URI schemes and communication problems. Servers MAY add [RFC4918] compliant DAV:response elements as content to the condition element indicating the precise reason for the failure. 2.3. The Successful 207 (Multistatus) Response If the server returns 207 (Multistatus), then the search proceeded successfully and the response MUST use the WebDAV multistatus format ([RFC4918], Section 13). The results of this method SHOULD NOT be cached. There MUST be one DAV:response for each resource that matched the search criteria. For each such response, the DAV:href element contains the URI of the resource, and the response MUST include a DAV:propstat element. Note: the WebDAV multistatus format requires at least one DAV: response child element. This specification relaxes that restriction so that empty results can be represented. Note that for each matching resource found there may be multiple URIs within the search scope mapped to it. In this case, a server SHOULD report only one of these URIs. Clients can use the live property DAV:resource-id defined in Section 3.1 of [draft-ietf-webdav-bind] to identify possible duplicates. 2.3.1. Result Set Truncation A server MAY limit the number of resources in a reply, for example to limit the amount of resources expended in processing a query. If it does so, the reply MUST use status code 207, return a DAV:multistatus response body and indicate a status of 507 (Insufficient Storage) for the search arbiter URI. It SHOULD include the partial results. When a result set is truncated, there may be many more resources that satisfy the search criteria but that were not examined. If partial results are included and the client requested an ordered result set in the original request, then any partial results that are returned MUST be ordered as the client directed. Note that the partial results returned MAY be any subset of the result set that would have satisfied the original query. Reschke, et al. Expires January 8, 2009 [Page 11]
Internet-Draft WebDAV SEARCH July 2008 2.3.2. Extending the PROPFIND Response A response MAY include more information than PROPFIND defines so long as the extra information does not invalidate the PROPFIND response. Query grammars SHOULD define how the response matches the PROPFIND response. 2.3.3. Example: A Simple Request and Response This example demonstrates the request and response framework. The following XML document shows a simple (hypothetical) natural language query. The name of the query element is natural-language-query in the XML namespace "http://example.com/foo". The actual query is "Find the locations of good Thai restaurants in Los Angeles". For this hypothetical query, the arbiter returns two properties for each selected resource. >> Request: SEARCH / HTTP/1.1 Host: example.org Content-Type: application/xml; charset="utf-8" Content-Length: 252 <?xml version="1.0" encoding="UTF-8"?> <D:searchrequest xmlns:D="DAV:" xmlns:F="http://example.com/foo"> <F:natural-language-query> Find the locations of good Thai restaurants in Los Angeles </F:natural-language-query> </D:searchrequest> Reschke, et al. Expires January 8, 2009 [Page 12]
Internet-Draft WebDAV SEARCH July 2008 >> Response: HTTP/1.1 207 Multi-Status Content-Type: text/xml; charset="utf-8" Content-Length: 429 <?xml version="1.0" encoding="UTF-8"?> <D:multistatus xmlns:D="DAV:" xmlns:R="http://example.org/propschema"> <D:response> <D:href>http://siamiam.example/</D:href> <D:propstat> <D:prop> <R:location>259 W. Hollywood</R:location> <R:rating><R:stars>4</R:stars></R:rating> </D:prop> <D:status>HTTP/1.1 200 OK</D:status> </D:propstat> </D:response> </D:multistatus> 2.3.4. Example: Result Set Truncation In the example below, the server returns just two results, and then indicates that the result is truncated by adding a DAV:response element for the search arbiter resource with 507 (Insufficient Storage) status. >> Request: SEARCH / HTTP/1.1 Host: example.net Content-Type: text/xml; charset="utf-8" Content-Length: xxx ... the query goes here ... Reschke, et al. Expires January 8, 2009 [Page 13]
Internet-Draft WebDAV SEARCH July 2008 >> Response: HTTP/1.1 207 Multistatus Content-Type: text/xml; charset="utf-8" Content-Length: 640 <?xml version="1.0" encoding="utf-8"?> <D:multistatus xmlns:D="DAV:"> <D:response> <D:href>http://www.example.net/sounds/unbrokenchain.au</D:href> <D:status>HTTP/1.1 200 OK</D:status> </D:response> <D:response> <D:href>http://tech.mit.example/arch96/photos/Lesh1.jpg</D:href> <D:status>HTTP/1.1 200 OK</D:status> </D:response> <D:response> <D:href>http://example.net</D:href> <D:status>HTTP/1.1 507 Insufficient Storage</D:status> <D:responsedescription xml:lang="en"> Only first two matching records were returned </D:responsedescription> </D:response> </D:multistatus> 2.4. Unsuccessful Responses If a SEARCH request could not be executed or the attempt to execute it resulted in an error, the server MUST indicate the failure with an appropriate status code and SHOULD add a response body as defined in [RFC3253], Section 1.6. Unless otherwise stated, condition elements are empty, however specific condition elements MAY include additional child elements that describe the error condition in more detail. 2.4.1. Example of an Invalid Scope In the example below, a request failed because the scope identifies a HTTP resource that was not found. Reschke, et al. Expires January 8, 2009 [Page 14]
Internet-Draft WebDAV SEARCH July 2008 >> Response: HTTP/1.1 409 Conflict Content-Type: text/xml; charset="utf-8" Content-Length: 275 <?xml version="1.0" encoding="UTF-8"?> <d:error xmlns:d="DAV:"> <d:search-scope-valid> <d:response> <d:href>http://www.example.com/X</d:href> <d:status>HTTP/1.1 404 Object Not Found</d:status> </d:response> </d:search-scope-valid> </d:error> 3. Discovery of Supported Query Grammars Servers MUST support discovery of the query grammars supported by a search arbiter resource. Clients can determine which query grammars are supported by an arbiter by invoking OPTIONS on the search arbiter. If the resource supports SEARCH, then the DASL response header will appear in the response. The DASL response header lists the supported grammars. Servers supporting the WebDAV extensions [RFC3253] and/or [RFC3744] MUST also o report SEARCH in the live property DAV:supported-method-set for all search arbiter resources and o support the live property DAV:supported-query-grammar-set as defined in Section 3.3. 3.1. The OPTIONS Method The OPTIONS method allows the client to discover if a resource supports the SEARCH method and to determine the list of search grammars supported for that resource. The client issues the OPTIONS method against a resource named by the Request-URI. This is a normal invocation of OPTIONS as defined in Section 9.2 of [RFC2616]. If a resource supports the SEARCH method, then the server MUST list SEARCH in the Allow header defined in Section 14.7 of [RFC2616]. Reschke, et al. Expires January 8, 2009 [Page 15]
Internet-Draft WebDAV SEARCH July 2008 DASL servers MUST include the DASL header in the OPTIONS response. This header identifies the search grammars supported by that resource. 3.2. The DASL Response Header DASLHeader = "DASL" ":" 1#Coded-URL Coded-URL = <defined in Section 10.1 of [RFC4918]> (This grammar uses the augmented BNF format defined in Section 2.1 of [RFC2616]) The DASL response header indicates server support for query grammars in the OPTIONS method. The value is a list of URIs that indicate the types of supported grammars. Note that although the URIs can be used to identify each supported search grammar, there is not necessarily a direct relationship between the URI and the XML element name that can be used in XML based SEARCH requests (the element name itself is identified by its namespace name (a URI reference) and the element's local name). Note: this header field value is defined as a comma-separated list ([RFC2616], Section 4.2), thus grammar URIs can appear in multiple header instances, separated by commas, or both. For example: DASL: <http://foobar.example/syntax1>, <http://akuma.example/syntax2>, <DAV:basicsearch> DASL: <http://example.com/foo/natural-language-query> 3.3. DAV:supported-query-grammar-set (protected) This WebDAV property is required for any server supporting either [RFC3253] and/or [RFC3744] and identifies the XML based query grammars that are supported by the search arbiter resource. <!ELEMENT supported-query-grammar-set (supported-query-grammar*)> <!ELEMENT supported-query-grammar (grammar)> <!ELEMENT grammar ANY> <!-- ANY value: a query grammar element type --> 3.4. Example: Grammar Discovery This example shows that the server supports search on the /somefolder resource with the query grammars: DAV:basicsearch, http://foobar.example/syntax1 and http://akuma.example/syntax2. Note that servers supporting WebDAV SEARCH MUST support DAV:basicsearch. Reschke, et al. Expires January 8, 2009 [Page 16]
Internet-Draft WebDAV SEARCH July 2008 >> Request: OPTIONS /somefolder HTTP/1.1 Host: example.org >> Response: HTTP/1.1 200 OK Allow: OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE, COPY, MOVE Allow: MKCOL, PROPFIND, PROPPATCH, LOCK, UNLOCK, SEARCH DASL: <DAV:basicsearch> DASL: <http://foobar.example/syntax1>, <http://akuma.example/syntax2> This example shows the equivalent taking advantage of a server's support for DAV:supported-method-set and DAV:supported-query-grammar- set. >> Request: PROPFIND /somefolder HTTP/1.1 Host: example.org Depth: 0 Content-Type: text/xml; charset="utf-8" Content-Length: 165 <?xml version="1.0" encoding="UTF-8" ?> <propfind xmlns="DAV:"> <prop> <supported-query-grammar-set/> <supported-method-set/> </prop> </propfind> Reschke, et al. Expires January 8, 2009 [Page 17]
Internet-Draft WebDAV SEARCH July 2008 >> Response: HTTP/1.1 207 Multi-Status Content-Type: text/xml; charset="utf-8" Content-Length: 1349 <?xml version="1.0" encoding="utf-8" ?> <multistatus xmlns="DAV:"> <response> <href>http://example.org/somefolder</href> <propstat> <prop> <supported-query-grammar-set> <supported-query-grammar> <grammar><basicsearch/></grammar> </supported-query-grammar> <supported-query-grammar> <grammar><syntax1 xmlns="http://foobar.example/"/></grammar> </supported-query-grammar> <supported-query-grammar> <grammar><syntax2 xmlns="http://akuma.example/"/></grammar> </supported-query-grammar> </supported-query-grammar-set> <supported-method-set> <supported-method name="COPY" /> <supported-method name="DELETE" /> <supported-method name="GET" /> <supported-method name="HEAD" /> <supported-method name="LOCK" /> <supported-method name="MKCOL" /> <supported-method name="MOVE" /> <supported-method name="OPTIONS" /> <supported-method name="POST" /> <supported-method name="PROPFIND" /> <supported-method name="PROPPATCH" /> <supported-method name="PUT" /> <supported-method name="SEARCH" /> <supported-method name="TRACE" /> <supported-method name="UNLOCK" /> </supported-method-set> </prop> <status>HTTP/1.1 200 OK</status> </propstat> </response> </multistatus> Note that the query grammar element names marshalled as part of the DAV:supported-query-grammar-set can be directly used as element names Reschke, et al. Expires January 8, 2009 [Page 18]
Internet-Draft WebDAV SEARCH July 2008 in an XML based query. 4. Query Schema Discovery: QSD Servers MAY support the discovery of the schema for a query grammar. The DASL response header and the DAV:supported-query-grammar-set property provide means for clients to discover the set of query grammars supported by a resource. This alone is not sufficient information for a client to generate a query. For example, the DAV: basicsearch grammar defines a set of queries consisting of a set of operators applied to a set of properties and values, but the grammar itself does not specify which properties may be used in the query. QSD for the DAV:basicsearch grammar allows a client to discover the set of properties that are searchable, selectable, and sortable. Moreover, although the DAV:basicsearch grammar defines a minimal set of operators, it is possible that a resource might support additional operators in a query. For example, a resource might support an optional operator that can be used to express content-based queries in a proprietary syntax. QSD allows a client to discover these operators and their syntax. The set of discoverable quantities will differ from grammar to grammar, but each grammar can define a means for a client to discover what can be discovered. In general, the schema for a given query grammar depends on both the resource (the arbiter) and the scope. A given resource might have access to one set of properties for one potential scope, and another set for a different scope. For example, consider a server able to search two distinct collections, one holding cooking recipes, the other design documents for nuclear weapons. While both collections might support properties such as author, title, and date, the first might also define properties such as calories and preparation time, while the second defined properties such as yield and applicable patents. Two distinct arbiters indexing the same collection might also have access to different properties. For example, the recipe collection mentioned above might also be indexed by a value-added server that also stored the names of chefs who had tested the recipe. Note also that the available query schema might also depend on other factors, such as the identity of the principal conducting the search, but these factors are not exposed in this protocol. 4.1. Additional SEARCH Semantics Each query grammar supported by DASL defines its own syntax for expressing the possible query schema. A client retrieves the schema for a given query grammar on an arbiter resource with a given scope by invoking the SEARCH method on that arbiter with that grammar and Reschke, et al. Expires January 8, 2009 [Page 19]
Internet-Draft WebDAV SEARCH July 2008 scope and with a root element of DAV:query-schema-discovery rather than DAV:searchrequest. Marshalling: The request body MUST be a DAV:query-schema-discovery element. <!ELEMENT query-schema-discovery ANY> <!-- ANY value: XML element specifying the query grammar and the scope --> The response body takes the form of a DAV:multistatus element ([RFC4918], Section 13), where DAV:response is extended to hold the returned query grammar inside a DAV:query-schema container element. <!ELEMENT response (href, status, query-schema?, responsedescription? > <!ELEMENT query-schema ANY> The content of this container is an XML element whose name and syntax depend upon the grammar, and whose value may (and likely will) vary depending upon the grammar, arbiter, and scope. 4.1.1. Example of Query Schema Discovery In this example, the arbiter is recipes.example, the grammar is DAV: basicsearch, the scope is also recipes.example. >> Request: SEARCH / HTTP/1.1 Host: recipes.example Content-Type: application/xml; charset="utf-8" Content-Length: 258 <?xml version="1.0"?> <query-schema-discovery xmlns="DAV:"> <basicsearch> <from> <scope> <href>http://recipes.example</href> <depth>infinity</depth> </scope> </from> </basicsearch> </query-schema-discovery> Reschke, et al. Expires January 8, 2009 [Page 20]
Internet-Draft WebDAV SEARCH July 2008 >> Response: HTTP/1.1 207 Multistatus Content-Type: application/xml; charset="utf-8" Content-Length: xxx <?xml version="1.0"?> <multistatus xmlns="DAV:"> <response> <href>http://recipes.example</href> <status>HTTP/1.1 200 OK</status> <query-schema> <basicsearchschema> <!-- (See Section 5.19 for the actual contents) --> </basicsearchschema> </query-schema> </response> </multistatus> The query schema for DAV:basicsearch is defined in Section 5.19. 5. The DAV:basicsearch Grammar 5.1. Introduction DAV:basicsearch uses an extensible XML syntax that allows clients to express search requests that are generally useful for WebDAV scenarios. DASL-extended servers MUST accept this grammar, and MAY accept other grammars. DAV:basicsearch has several components: o DAV:select provides the result record definition. o DAV:from defines the scope. o DAV:where defines the criteria. o DAV:orderby defines the sort order of the result set. o DAV:limit provides constraints on the query as a whole. Reschke, et al. Expires January 8, 2009 [Page 21]
Internet-Draft WebDAV SEARCH July 2008 5.2. The DAV:basicsearch DTD <!-- "basicsearch" element --> <!ELEMENT basicsearch (select, from, where?, orderby?, limit?) > <!-- "select" element --> <!ELEMENT select (allprop | prop) > <!-- "from" element --> <!ELEMENT from (scope+) > <!ELEMENT scope (href, depth, include-versions?) > <!ELEMENT include-versions EMPTY > <!-- "where" element --> Reschke, et al. Expires January 8, 2009 [Page 22]
Internet-Draft WebDAV SEARCH July 2008 <!ENTITY % comp_ops "eq | lt | gt| lte | gte"> <!ENTITY % log_ops "and | or | not"> <!ENTITY % special_ops "is-collection | is-defined | language-defined | language-matches"> <!ENTITY % string_ops "like"> <!ENTITY % content_ops "contains"> <!ENTITY % all_ops "%comp_ops; | %log_ops; | %special_ops; | %string_ops; | %content_ops;"> <!ELEMENT where ( %all_ops; ) > <!ELEMENT and ( %all_ops; )+ > <!ELEMENT or ( %all_ops; )+ > <!ELEMENT not ( %all_ops; ) > <!ELEMENT lt (prop, (literal|typed-literal)) > <!ATTLIST lt caseless (yes|no) #IMPLIED> <!ELEMENT lte (prop, (literal|typed-literal)) > <!ATTLIST lte caseless (yes|no) #IMPLIED> <!ELEMENT gt (prop, (literal|typed-literal)) > <!ATTLIST gt caseless (yes|no) #IMPLIED> <!ELEMENT gte (prop, (literal|typed-literal)) > <!ATTLIST gte caseless (yes|no) #IMPLIED> <!ELEMENT eq (prop, (literal|typed-literal)) > <!ATTLIST eq caseless (yes|no) #IMPLIED> <!ELEMENT literal (#PCDATA)> <!ELEMENT typed-literal (#PCDATA)> <!ATTLIST typed-literal xsi:type CDATA #IMPLIED> <!ELEMENT is-collection EMPTY > <!ELEMENT is-defined (prop) > <!ELEMENT language-defined (prop) > <!ELEMENT language-matches (prop, literal) > <!ELEMENT like (prop, literal) > <!ATTLIST like caseless (yes|no) #IMPLIED> <!ELEMENT contains (#PCDATA)> Reschke, et al. Expires January 8, 2009 [Page 23]
Internet-Draft WebDAV SEARCH July 2008 <!-- "orderby" element --> <!ELEMENT orderby (order+) > <!ELEMENT order ((prop | score), (ascending | descending)?)> <!ATTLIST order caseless (yes|no) #IMPLIED> <!ELEMENT ascending EMPTY> <!ELEMENT descending EMPTY> <!-- "limit" element --> <!ELEMENT limit (nresults) > <!ELEMENT nresults (#PCDATA) > 5.2.1. Example Query This query retrieves the content length values for all resources located under the server's "/container1/" URI namespace whose length exceeds 10000 sorted ascending by size. <d:searchrequest xmlns:d="DAV:"> <d:basicsearch> <d:select> <d:prop><d:getcontentlength/></d:prop> </d:select> <d:from> <d:scope> <d:href>/container1/</d:href> <d:depth>infinity</d:depth> </d:scope> </d:from> <d:where> <d:gt> <d:prop><d:getcontentlength/></d:prop> <d:literal>10000</d:literal> </d:gt> </d:where> <d:orderby> <d:order> <d:prop><d:getcontentlength/></d:prop> <d:ascending/> </d:order> </d:orderby> </d:basicsearch> </d:searchrequest> Reschke, et al. Expires January 8, 2009 [Page 24]
Internet-Draft WebDAV SEARCH July 2008 5.3. DAV:select DAV:select defines the result record, which is a set of properties and values. This document defines two possible values: DAV:allprop and DAV:prop, both defined in Section 14 of [RFC4918]. 5.4. DAV:from <!ELEMENT scope (href, depth, include-versions?) > <!ELEMENT include-versions EMPTY > DAV:from defines the query scope. This contains one or more DAV: scope elements. Support for multiple scope elements is optional, however servers MUST fail a request specifying multiple DAV:scope elements if they can't support it (see Section 2.2.2, precondition DAV:search-multiple-scope-supported). The scope element contains mandatory DAV:href and DAV:depth elements. DAV:href indicates the URI reference ([RFC3986], Section 4.1) to use as a scope. When the scope is a collection, if DAV:depth is "0", the search includes only the collection. When it is "1", the search includes the collection and its immediate children. When it is "infinity", it includes the collection and all its progeny. When the scope is not a collection, the depth is ignored and the search applies just to the resource itself. If the server supports WebDAV Redirect Reference Resources ([RFC4437]) and the search scope contains a redirect reference resource, then it applies only to that resource, not to its target. When the child element DAV:include-versions is present, the search scope will include all versions (see [RFC3253], Section 2.2.1) of all version-controlled resources in scope. Servers that do support versioning but do not support the DAV:include-versions feature MUST signal an error if it is used in a query (see Section 2.2.2, precondition DAV:search-scope-valid). 5.4.1. Relationship to the Request-URI If the DAV:scope element is an URI ([RFC3986], Section 3), the scope is exactly that URI. If the DAV:scope element is a relative reference ([RFC3986], Section 4.2), the scope is taken to be relative to the Request-URI. Reschke, et al. Expires January 8, 2009 [Page 25]
Internet-Draft WebDAV SEARCH July 2008 5.4.2. Scope A Scope can be an arbitrary URI reference. Servers, of course, may support only particular scopes. This may include limitations for particular schemes such as "http:" or "ftp:" or certain URI namespaces. However, WebDAV compliant search arbiters minimally SHOULD support scopes that match their own URI. 5.5. DAV:where The DAV:where element defines the search condition for inclusion of resources in the result set. The value of this element is an XML element that defines a search operator that evaluates to one of the Boolean truth values TRUE, FALSE, or UNKNOWN. The search operator contained by DAV:where may itself contain and evaluate additional search operators as operands, which in turn may contain and evaluate additional search operators as operands, etc. recursively. 5.5.1. Use of Three-Valued Logic in Queries Each operator defined for use in the where clause that returns a Boolean value MUST evaluate to TRUE, FALSE, or UNKNOWN. The resource under scan is included as a member of the result set if and only if the search condition evaluates to TRUE. Consult Appendix A for details on the application of three-valued logic in query expressions. 5.5.2. Handling Optional Operators If a query contains an operator that is not supported by the server, then the server MUST respond with a 422 (Unprocessable Entity) status code. 5.5.3. Treatment of NULL Values If a PROPFIND for a property value would yield a non-2xx (see [RFC2616], Section 10.2) response for that property, then that property is considered NULL. NULL values are "less than" all other values in comparisons. Empty strings (zero length strings) are not NULL values. An empty string is "less than" a string with length greater than zero. The DAV:is-defined operator is defined to test if the value of a property is not NULL. Reschke, et al. Expires January 8, 2009 [Page 26]
Internet-Draft WebDAV SEARCH July 2008 5.5.4. Treatment of Properties with mixed/element Content Comparisons of properties that do not have simple types (text-only content) is out-of-scope for the standard operators defined for DAV: basicsearch and therefore is defined to be UNKNOWN (as per Appendix A). For querying the DAV:resourcetype property, see Section 5.13. 5.5.5. Example: Testing for Equality The example shows a single operator (DAV:eq) applied in the criteria. <d:where> <d:eq> <d:prop> <d:getcontentlength/> </d:prop> <d:literal>100</d:literal> </d:eq> </d:where> 5.5.6. Example: Relative Comparisons The example shows a more complex operation involving several operators (DAV:and, DAV:eq, DAV:gt) applied in the criteria. This DAV:where expression matches those resources of type "image/gif" over 4K in size. <D:where> <D:and> <D:eq> <D:prop> <D:getcontenttype/> </D:prop> <D:literal>image/gif</D:literal> </D:eq> <D:gt> <D:prop> <D:getcontentlength/> </D:prop> <D:literal>4096</D:literal> </D:gt> </D:and> </D:where> Reschke, et al. Expires January 8, 2009 [Page 27]
Internet-Draft WebDAV SEARCH July 2008 5.6. DAV:orderby The DAV:orderby element specifies the ordering of the result set. It contains one or more DAV:order elements, each of which specifies a comparison between two items in the result set. Informally, a comparison specifies a test that determines whether one resource appears before another in the result set. Comparisons are applied in the order they occur in the DAV:orderby element, earlier comparisons being more significant. The comparisons defined here use only a single property from each resource, compared using the same ordering as the DAV:lt operator (ascending) or DAV:gt operator (descending). If neither direction is specified, the default is DAV:ascending. In the context of the DAV:orderby element, null values are considered to collate before any actual (i.e., non null) value, including strings of zero length (this is compatible with [SQL99]). The "caseless" attribute may be used to indicate case-sensitivity for comparisons (Section 5.18). 5.6.1. Example of Sorting This sort orders first by last name of the author, and then by size, in descending order, so that for each author, the largest works appear first. <d:orderby> <d:order> <d:prop><r:lastname/></d:prop> <d:ascending/> </d:order> <d:order> <d:prop><d:getcontentlength/></d:prop> <d:descending/> </d:order> </d:orderby> 5.7. Boolean Operators: DAV:and, DAV:or, and DAV:not The DAV:and operator performs a logical AND operation on the expressions it contains. The DAV:or operator performs a logical OR operation on the values it contains. The DAV:not operator performs a logical NOT operation on the values Reschke, et al. Expires January 8, 2009 [Page 28]
Internet-Draft WebDAV SEARCH July 2008 it contains. 5.8. DAV:eq The DAV:eq operator provides simple equality matching on property values. The "caseless" attribute may be used with this element (Section 5.18). 5.9. DAV:lt, DAV:lte, DAV:gt, DAV:gte The DAV:lt, DAV:lte, DAV:gt, and DAV:gte operators provide comparisons on property values, using less-than, less-than or equal, greater-than, and greater-than or equal respectively. The "caseless" attribute may be used with these elements (Section 5.18). 5.10. DAV:literal DAV:literal allows literal values to be placed in an expression. White space in literal values is significant in comparisons. For consistency with [RFC4918], clients SHOULD NOT specify the attribute "xml:space" (Section 2.10 of [XML]) to override this behavior. In comparisons, the contents of DAV:literal SHOULD be treated as string, with the following exceptions: o when operand for a comparison with a DAV:getcontentlength property, it SHOULD be treated as an unsigned integer value (the behavior for values not in this format is undefined), o when operand for a comparison with a DAV:creationdate or DAV: getlastmodified property, it SHOULD be treated as a date value in the ISO-8601 subset defined for the DAV:creationdate property (see [RFC4918], Section 15.1; the behavior of values not in this format is undefined), o when operand for a comparison with a property for which the type is known and when compatible with that type, it MAY be treated according to this type. 5.11. DAV:typed-literal (optional) There are situations in which a client may want to force a comparison not to be string-based (as defined for DAV:literal). In these cases, a typed comparison can be enforced by using DAV:typed-literal instead. Reschke, et al. Expires January 8, 2009 [Page 29]
Internet-Draft WebDAV SEARCH July 2008 <!ELEMENT typed-literal (#PCDATA)> The data type is specified using the xsi:type attribute defined in [XS1], Section 2.6.1. If the type is not specified, it defaults to "xs:string". A server MUST reject a request with an unknown type with a status of 422 (Unprocessable Entity). It SHOULD reject a request if the value provided in DAV:typed-literal can not be cast to the specified type. The comparison evaluates to UNKNOWN if the property value can not be cast to the specified datatype (see [XPATHFUNC], Section 17). 5.11.1. Example for Typed Numerical Comparison Consider a set of resources with the dead property "edits" in the namespace "http://ns.example.org": +-----+----------------+ | URI | property value | +-----+----------------+ | /a | "-1" | | /b | "01" | | /c | "3" | | /d | "test" | | /e | (undefined) | +-----+----------------+ The expression <lt xmlns="DAV:" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xs="http://www.w3.org/2001/XMLSchema"> <prop><edits xmlns="http://ns.example.org"/></prop> <typed-literal xsi:type="xs:integer">3</typed-literal> </lt> will evaluate to TRUE for the resources "/a" and "/b" (their property values can be parsed as type xs:integer, and the numerical comparison evaluates to true), to FALSE for "/c" (property value is compatible, but numerical comparison evaluates to false) and UNKNOWN for "/d" and "/e" (the property either is undefined, or its value can not be parsed as xs:integer). 5.12. Support for Matching xml:lang Attributes on Properties The following two optional operators can be used to express conditions on the language of a property value (as expressed using Reschke, et al. Expires January 8, 2009 [Page 30]
Internet-Draft WebDAV SEARCH July 2008 the xml:lang attribute). 5.12.1. DAV:language-defined (optional) <!ELEMENT language-defined (prop)> This operator evaluates to TRUE if the language for the value of the given property is known, FALSE if it isn't and UNKNOWN if the property itself is not defined. 5.12.2. DAV:language-matches (optional) <!ELEMENT language-matches (prop, literal)> This operator evaluates to TRUE if the language for the value of the given property is known and matches the language name given in the <literal> element, FALSE if it doesn't match and UNKNOWN if the property itself is not defined. Languages are considered to match if they are the same, or if the language of the property value is a sublanguage of the language specified in the <literal> element (see [XPATH], Section 4.3, "lang function"). 5.12.3. Example of Language-Aware Matching The expression below will evaluate to TRUE if the property "foobar" exists and its language is either unknown, English or a sublanguage of English. <or xmlns="DAV:"> <not> <language-defined> <prop><foobar/></prop> </language-defined> </not> <language-matches> <prop><foobar/></prop> <literal>en</literal> </language-matches> </or> 5.13. DAV:is-collection The DAV:is-collection operator allows clients to determine whether a resource is a collection (that is, whether its DAV:resourcetype element contains the element DAV:collection). Reschke, et al. Expires January 8, 2009 [Page 31]
Internet-Draft WebDAV SEARCH July 2008 Rationale: This operator is provided in lieu of defining generic structure queries, which would suffice for this and for many more powerful queries, but seems inappropriate to standardize at this time. 5.13.1. Example of DAV:is-collection This example shows a search criterion that picks out all and only the resources in the scope that are collections. <where xmlns="DAV:"> <is-collection/> </where> 5.14. DAV:is-defined The DAV:is-defined operator allows clients to determine whether a property is defined on a resource. The meaning of "defined on a resource" is found in Section 5.5.3. Example: <d:is-defined> <d:prop><x:someprop/></d:prop> </d:is-defined> 5.15. DAV:like The DAV:like is an optional operator intended to give simple wildcard-based pattern matching ability to clients. The operator takes two arguments. The first argument is a DAV:prop element identifying a single property to evaluate. The second argument is a DAV:literal element that gives the pattern matching string. Reschke, et al. Expires January 8, 2009 [Page 32]
Internet-Draft WebDAV SEARCH July 2008 5.15.1. Syntax for the Literal Pattern pattern = [wildcard] 0*( text [wildcard] ) wildcard = exactlyone / zeroormore text = 1*( character / escapeseq ) exactlyone = "_" zeroormore = "%" escapechar = "\" escapeseq = escapechar ( exactlyone / zeroormore / escapechar ) ; character: see [XML], Section 2.2, minus wildcard / escapechar character = HTAB / LF / CR ; whitespace character =/ %x20-24 / %x26-5B / %x5D-5E / %x60-D7FF character =/ %xE000-FFFD / %x10000-10FFFF (Note that the ABNF above is defined in terms of Unicode code points ([UNICODE5]); when an query is transmitted as XML document WebDAV, these characters are typically encoded in UTF-8 or UTF-16.) The value for the literal is composed of wildcards separated by segments of text. Wildcards may begin or end the literal. The "_" wildcard matches exactly one character. The "%" wildcard matches zero or more characters The "\" character is an escape sequence so that the literal can include "_" and "%". To include the "\" character in the pattern, the escape sequence "\\" is used. 5.15.2. Example of DAV:like This example shows how a client might use DAV:like to identify those resources whose content type was a subtype of image. <D:where> <D:like caseless="yes"> <D:prop><D:getcontenttype/></D:prop> <D:literal>image/%</D:literal> </D:like> </D:where> 5.16. DAV:contains The DAV:contains operator is an optional operator that provides content-based search capability. This operator implicitly searches Reschke, et al. Expires January 8, 2009 [Page 33]
Internet-Draft WebDAV SEARCH July 2008 against the text content of a resource, not against content of properties. The DAV:contains operator is intentionally not overly constrained, in order to allow the server to do the best job it can in performing the search. The DAV:contains operator evaluates to a Boolean value. It evaluates to TRUE if the content of the resource satisfies the search. Otherwise, it evaluates to FALSE. Within the DAV:contains XML element, the client provides a phrase: a single word or whitespace delimited sequence of words. Servers MAY ignore punctuation in a phrase. Case-sensitivity is at the discretion of the server implementation. The following non-exhaustive list enumerate things that may or may not be done as part of the search: Phonetic methods such as "soundex" may or may not be used. Word stemming may or may not be performed. Thesaurus expansion of words may or may not be done. Right or left truncation may or may not be performed. The search may be case insensitive or case sensitive. The word or words may or may not be interpreted as names. Multiple words may or may not be required to be adjacent or "near" each other. Multiple words may or may not be required to occur in the same order. Multiple words may or may not be treated as a phrase. The search may or may not be interpreted as a request to find documents "similar" to the string operand. Character canonicalization such as that done by the Unicode collation algorithm may or may not be applied. 5.16.1. Result Scoring (DAV:score Element) Servers SHOULD indicate scores for the DAV:contains condition by adding a DAV:score XML element to the DAV:response element. Its value is defined only in the context of a particular query result. The value is a string representing the score, an integer from zero to 10000 inclusive, where a higher value indicates a higher score (e.g. more relevant). Modified DTD fragment for DAV:propstat: <!ELEMENT response (href, ((href*, status)|(propstat+)), responsedescription?, score?) > <!ELEMENT score (#PCDATA) > Clients should note that, in general, it is not meaningful to compare the numeric values of scores from two different query results unless both were executed by the same underlying search system on the same collection of resources. Reschke, et al. Expires January 8, 2009 [Page 34]
Internet-Draft WebDAV SEARCH July 2008 5.16.2. Ordering by Score To order search results by their score, the DAV:score element may be added as child to the DAV:orderby element (in place of a DAV:prop element). 5.16.3. Examples The example below shows a search for the phrase "Peter Forsberg". Depending on its support for content-based searching, a server MAY treat this as a search for documents that contain the words "Peter" and "Forsberg". <D:where> <D:contains>Peter Forsberg</D:contains> </D:where> The example below shows a search for resources that contain "Peter" and "Forsberg". <D:where> <D:and> <D:contains>Peter</D:contains> <D:contains>Forsberg</D:contains> </D:and> </D:where> 5.17. Limiting the Result Set <!ELEMENT limit (nresults) > <!ELEMENT nresults (#PCDATA)> <!-- only digits --> The DAV:limit XML element contains requested limits from the client to limit the size of the reply or amount of effort expended by the server. The DAV:nresults XML element contains a requested maximum number of DAV:response elements to be returned in the response body. The server MAY disregard this limit. The value of this element is an unsigned integer. 5.17.1. Relationship to Result Ordering If the result set is both limited by DAV:limit and ordered according to DAV:orderby, the results that are included in the response document must be those that order highest. Reschke, et al. Expires January 8, 2009 [Page 35]
Internet-Draft WebDAV SEARCH July 2008 5.18. The 'caseless' XML Attribute The "caseless" attribute allows clients to specify caseless matching behavior instead of character-by-character matching for DAV: basicsearch operators. The possible values for "caseless" are "yes" or "no". The default value is server-specified. Caseless matching SHOULD be implemented as defined in Section 5.18 of the Unicode Standard ([UNICODE5]). Support for the "caseless" attribute is optional. A server should respond with a status of 422 if it is used but cannot be supported. 5.19. Query Schema for DAV:basicsearch The DAV:basicsearch grammar defines a search criteria that is a Boolean-valued expression, and allows for an arbitrary set of properties to be included in the result record. The result set may be sorted on a set of property values. Accordingly the DTD for schema discovery for this grammar allows the server to express: 1. the set of properties that may be either searched, returned, or used to sort, and a hint about the data type of such properties 2. the set of optional operators defined by the resource. 5.19.1. DTD for DAV:basicsearch QSD <!ELEMENT basicsearchschema (properties, operators)> <!ELEMENT any-other-property EMPTY> <!ELEMENT properties (propdesc*)> <!ELEMENT propdesc ((prop|any-other-property), datatype?, searchable?, selectable?, sortable?, caseless?)> <!ELEMENT operators (opdesc*)> <!ELEMENT opdesc ANY> <!ATTLIST opdesc allow-pcdata (yes|no) #IMPLIED> <!ELEMENT operand-literal EMPTY> <!ELEMENT operand-typed-literal EMPTY> <!ELEMENT operand-property EMPTY> The DAV:properties element holds a list of descriptions of properties. The DAV:operators element describes the optional operators that may be used in a DAV:where element. Reschke, et al. Expires January 8, 2009 [Page 36]
Internet-Draft WebDAV SEARCH July 2008 5.19.2. DAV:propdesc Element Each instance of a DAV:propdesc element describes the property or properties in the DAV:prop element it contains. All subsequent elements are descriptions that apply to those properties. All descriptions are optional and may appear in any order. Servers SHOULD support all the descriptions defined here, and MAY define others. DASL defines five descriptions. The first, DAV:datatype, provides a hint about the type of the property value, and may be useful to a user interface prompting for a value. The remaining four (DAV: searchable, DAV:selectable, DAV:sortable, and DAV:caseless) identify portions of the query (DAV:where, DAV:select, and DAV:orderby, respectively). If a property has a description for a section, then the server MUST allow the property to be used in that section. These descriptions are optional. If a property does not have such a description, or is not described at all, then the server MAY still allow the property to be used in the corresponding section. 5.19.2.1. DAV:any-other-property This element can be used in place of DAV:prop to describe properties of WebDAV properties not mentioned in any other DAV:prop element. For instance, this can be used to indicate that all other properties are searchable and selectable without giving details about their types (a typical scenario for dead properties). 5.19.3. The DAV:datatype Property Description The DAV:datatype element contains a single XML element that provides a hint about the domain of the property, which may be useful to a user interface prompting for a value to be used in a query. Data types are identified by an element name. Where appropriate, a server SHOULD use the simple data types defined in [XS2]. <!ELEMENT datatype ANY > Examples from [XS2], Section 3: +----------------+---------------------+ | Qualified name | Example | +----------------+---------------------+ | xs:boolean | true, false, 1, 0 | | xs:string | Foobar | | xs:dateTime | 1994-11-05T08:15:5Z | | xs:float | .314159265358979E+1 | Reschke, et al. Expires January 8, 2009 [Page 37]
Internet-Draft WebDAV SEARCH July 2008 | xs:integer | -259, 23 | +----------------+---------------------+ If the data type of a property is not given, then the data type defaults to xs:string. 5.19.4. The DAV:searchable Property Description <!ELEMENT searchable EMPTY> If this element is present, then the server MUST allow this property to appear within a DAV:where element where an operator allows a property. Allowing a search does not mean that the property is guaranteed to be defined on every resource in the scope, it only indicates the server's willingness to check. 5.19.5. The DAV:selectable Property Description <!ELEMENT selectable EMPTY> This element indicates that the property may appear in the DAV:select element. 5.19.6. The DAV:sortable Property Description This element indicates that the property may appear in the DAV: orderby element. <!ELEMENT sortable EMPTY> 5.19.7. The DAV:caseless Property Description This element only applies to properties whose data type is "xs: string" and derived data types as per the DAV:datatype property description. Its presence indicates that compares performed for searches, and the comparisons for ordering results on the string property will be caseless (the default is character-by-character). <!ELEMENT caseless EMPTY> 5.19.8. The DAV:operators XML Element The DAV:operators element describes every optional operator supported in a query. (Mandatory operators are not listed since they are mandatory and permit no variation in syntax.). All optional operators that are supported MUST be listed in the DAV:operators element. Reschke, et al. Expires January 8, 2009 [Page 38]
Internet-Draft WebDAV SEARCH July 2008 The listing for an operator, contained in an DAV:opdesc element, consists of the operator (as an empty element), followed by one element for each operand. The operand MUST be either DAV:operand- property, DAV:operand-literal or DAV:operand-typed-literal, which indicate that the operand in the corresponding position is a property, a literal value or a typed literal value, respectively. If an operator is polymorphic (allows more than one operand syntax) then each permitted syntax MUST be listed separately. The DAV:opdesc element MAY have a "allow-pcdata" attribute (defaulting to "no"). A value of "yes" indicates that the operator can contain character data, as it is the case with DAV:contains (see Section 5.16). Definition of additional operators using this format is NOT RECOMMENDED. <operators xmlns='DAV:'> <opdesc> <like/><operand-property/><operand-literal/> </opdesc> </operators> Reschke, et al. Expires January 8, 2009 [Page 39]
Internet-Draft WebDAV SEARCH July 2008 5.19.9. Example of Query Schema for DAV:basicsearch <D:basicsearchschema xmlns:D="DAV:" xmlns:xs="http://www.w3.org/2001/XMLSchema""> <D:properties> <D:propdesc> <D:prop><D:getcontentlength/></D:prop> <D:datatype><xs:nonNegativeInteger/></D:datatype> <D:searchable/><D:selectable/><D:sortable/> </D:propdesc> <D:propdesc> <D:prop><D:getcontenttype/><D:displayname/></D:prop> <D:searchable/><D:selectable/><D:sortable/> </D:propdesc> <D:propdesc> <D:prop><fstop xmlns="http://jennicam.org"/></D:prop> <D:selectable/> </D:propdesc> <D:propdesc> <D:any-other-property/> <D:searchable/><D:selectable/> </D:propdesc> </D:properties> <D:operators> <D:opdesc> <D:like/><D:operand-property/><D:operand-literal/> </D:opdesc> <D:opdesc allow-pcdata="yes"> <D:contains/> </D:opdesc> </D:operators> </D:basicsearchschema> This response lists four properties. The data type of the last three properties is not given, so it defaults to xs:string. All are selectable, and the first three may be searched. All but the last may be used in a sort. Of the optional DAV operators, DAV:contains and DAV:like are supported. Note: The schema discovery defined here does not provide for discovery of supported values of the "caseless" attribute. This may require that the reply also list the mandatory operators. 6. Internationalization Considerations Properties may be language-tagged using the xml:lang attribute (see [RFC4918], Section 4.3). The optional operators DAV:language-defined Reschke, et al. Expires January 8, 2009 [Page 40]
Internet-Draft WebDAV SEARCH July 2008 (Section 5.12.1) and DAV:language-matches (Section 5.12.2) allow to express conditions on the language tagging information. 7. Security Considerations This section is provided to detail issues concerning security implications of which DASL applications need to be aware. All of the security considerations of HTTP/1.1 ([RFC2616] and WebDAV ([RFC4918]) also apply to DASL. In addition, this section will include security risks inherent in searching and retrieval of resource properties and content. A query MUST NOT allow clients to retrieve information that wouldn't have been available through the GET or PROPFIND methods in the first place. In particular: o Query constraints on WebDAV properties for which the client does not have read access need to be evaluated as if the property did not exist (see Section 5.5.3). o Query constraints on content (as with DAV:contains, defined in Section 5.16) for which the client does not have read access need to be evaluated as if a GET would return a 4xx status code. A server should prepare for denial of service attacks. For example a client may issue a query for which the result set is expensive to calculate or transmit because many resources match or must be evaluated. 7.1. Implications of XML External Entities XML supports a facility known as "external entities", defined in Section 4.2.2 of [XML], which instruct an XML processor to retrieve and perform an inline include of XML located at a particular URI. An external XML entity can be used to append or modify the document type declaration (DTD) associated with an XML document. An external XML entity can also be used to include XML within the content of an XML document. For non-validating XML, such as the XML used in this specification, including an external XML entity is not required by [XML]. However, [XML] does state that an XML processor may, at its discretion, include the external XML entity. External XML entities have no inherent trustworthiness and are subject to all the attacks that are endemic to any HTTP GET request. Furthermore, it is possible for an external XML entity to modify the DTD, and hence affect the final form of an XML document, in the worst case significantly modifying its semantics, or exposing the XML Reschke, et al. Expires January 8, 2009 [Page 41]
Internet-Draft WebDAV SEARCH July 2008 processor to the security risks discussed in [RFC3023]. Therefore, implementers must be aware that external XML entities should be treated as untrustworthy. There is also the scalability risk that would accompany a widely deployed application which made use of external XML entities. In this situation, it is possible that there would be significant numbers of requests for one external XML entity, potentially overloading any server which fields requests for the resource containing the external XML entity. 8. Scalability Query grammars are identified by URIs. Applications SHOULD not attempt to retrieve these URIs even if they appear to be retrievable (for example, those that begin with "http://") 9. IANA Considerations This document uses the namespace defined in Section 21 of [RFC4918] for XML elements. 9.1. HTTP Headers This document specifies the HTTP header listed below, to be added to the HTTP header registry defined in [RFC3864]. 9.1.1. DASL Header field name: DASL Applicable protocol: http Status: Experimental Author/Change controller: IETF Specification document: this specification (Section 3.2) 10. Contributors This document is based on prior work on the DASL protocol done by the WebDAV DASL working group until the year 2000 -- namely by Alan Babich, Jim Davis, Rick Henderson, Dale Lowry, Saveen Reddy and Surendra Reddy. Reschke, et al. Expires January 8, 2009 [Page 42]
Internet-Draft WebDAV SEARCH July 2008 11. Acknowledgements This document has benefited from thoughtful discussion by Lisa Dusseault, Javier Godoy, Sung Kim, Chris Newman, Elias Sinderson, Martin Wallmer, Keith Wannamaker, Jim Whitehead and Kevin Wiggen. 12. References 12.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2616] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. [RFC3023] Makoto, M., St.Laurent, S., and D. Kohn, "XML Media Types", RFC 3023, January 2001. [RFC3253] Clemm, G., Amsden, J., Ellison, T., Kaler, C., and J. Whitehead, "Versioning Extensions to WebDAV", RFC 3253, March 2002. [RFC3744] Clemm, G., Reschke, J., Sedlar, E., and J. Whitehead, "Web Distributed Authoring and Versioning (WebDAV) Access Control Protocol", RFC 3744, May 2004. [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. [RFC4918] Dusseault, L., Ed., "HTTP Extensions for Web Distributed Authoring and Versioning (WebDAV)", RFC 4918, June 2007. [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. [XML] Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E., and F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fourth Edition)", W3C REC-xml-20060816, August 2006, <http://www.w3.org/TR/2006/REC-xml-20060816>. [XPATH] Clark, J. and S. DeRose, "XML Path Language (XPath) Version 1.0", W3C REC-xpath-19991116, November 1999, <http://www.w3.org/TR/1999/REC-xpath-19991116>. Reschke, et al. Expires January 8, 2009 [Page 43]
Internet-Draft WebDAV SEARCH July 2008 [XPATHFUNC] Malhotra, A., Melton, J., and N. Walsh, "XQuery 1.0 and XPath 2.0 Functions and Operators", W3C REC-xpath- functions-20070123, January 2007, <http://www.w3.org/TR/2007/REC-xpath-functions-20070123/>. [XS1] Thompson, H., Beech, D., Maloney, M., Mendelsohn, N., and World Wide Web Consortium, "XML Schema Part 1: Structures", W3C REC-xmlschema-1-20041028, October 2004, <http://www.w3.org/TR/2004/REC-xmlschema-1-20041028/>. [XS2] Biron, P., Malhotra, A., and World Wide Web Consortium, "XML Schema Part 2: Datatypes Second Edition", W3C REC- xmlschema-2-20041028, October 2004, <http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/>. 12.2. Informative References [BCP47] Phillips, A. and M. Davis, "Matching of Language Tags", BCP 47, RFC 4647, September 2006. [DASL] Reddy, S., Lowry, D., Reddy, S., Henderson, R., Davis, J., and A. Babich, "DAV Searching & Locating", draft-ietf-dasl-protocol-00 (work in progress), July 1999. [DASLREQ] Davis, J., Reddy, S., and J. Slein, "Requirements for DAV Searching and Locating", February 1999, <http:// www.webdav.org/dasl/requirements/ draft-dasl-requirements-01.html>. This is an updated version of the Internet Draft "draft-ietf-dasl-requirements-00", but obviously never was submitted to the IETF. [RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration Procedures for Message Header Fields", BCP 90, RFC 3864, September 2004. [RFC4437] Whitehead, J., Clemm, G., and J. Reschke, Ed., "Web Distributed Authoring and Versioning (WebDAV) Redirect Reference Resources", RFC 4437, March 2006. [RFC4790] Newman, C., Duerst, M., and A. Gulbrandsen, "Internet Application Protocol Collation Registry", RFC 4790, March 2007. [SQL99] Milton, J., "Database Language SQL Part 2: Foundation (SQL/Foundation)", ISO ISO/IEC 9075-2:1999 (E), July 1999. Reschke, et al. Expires January 8, 2009 [Page 44]
Internet-Draft WebDAV SEARCH July 2008 [UNICODE5] The Unicode Consortium, "The Unicode Standard - Version 5.0", Addison-Wesley , November 2006, <http://www.unicode.org/versions/Unicode5.0.0/>. ISBN 0321480910 [1] [draft-ietf-webdav-bind] Clemm, G., Crawford, J., Reschke, J., Ed., and J. Whitehead, "Binding Extensions to Web Distributed Authoring and Versioning (WebDAV)", draft-ietf-webdav-bind-20 (work in progress), November 2007. URIs [1] <urn:isbn:0321480910> Appendix A. Three-Valued Logic in DAV:basicsearch ANSI standard three valued logic is used when evaluating the search condition (as defined in the ANSI standard SQL specifications, for example in ANSI X3.135-1992, section 8.12, pp. 188-189, section 8.2, p. 169, General Rule 1)a), etc.). ANSI standard three valued logic is undoubtedly the most widely practiced method of dealing with the issues of properties in the search condition not having a value (e.g., being null or not defined) for the resource under scan, and with undefined expressions in the search condition (e.g., division by zero, etc.). Three valued logic works as follows. Undefined expressions are expressions for which the value of the expression is not defined. Undefined expressions are a completely separate concept from the truth value UNKNOWN, which is, in fact, well defined. Property names and literal constants are considered expressions for purposes of this section. If a property in the current resource under scan has not been set to a value, then the value of that property is undefined for the resource under scan. DASL 1.0 has no arithmetic division operator, but if it did, division by zero would be an undefined arithmetic expression. If any subpart of an arithmetic, string, or datetime subexpression is undefined, the whole arithmetic, string, or datetime subexpression is undefined. There are no manifest constants to explicitly represent undefined Reschke, et al. Expires January 8, 2009 [Page 45]
Internet-Draft WebDAV SEARCH July 2008 number, string, or datetime values. Since a Boolean value is ultimately returned by the search condition, arithmetic, string, and datetime expressions are always arguments to other operators. Examples of operators that convert arithmetic, string, and datetime expressions to Boolean values are the six relational operators ("greater than", "less than", "equals", etc.). If either or both operands of a relational operator have undefined values, then the relational operator evaluates to UNKNOWN. Otherwise, the relational operator evaluates to TRUE or FALSE, depending upon the outcome of the comparison. The Boolean operators DAV:and, DAV:or and DAV:not are evaluated according to the following rules: not UNKNOWN = UNKNOWN UNKNOWN and TRUE = UNKNOWN UNKNOWN and FALSE = FALSE UNKNOWN and UNKNOWN = UNKNOWN UNKNOWN or TRUE = TRUE UNKNOWN or FALSE = UNKNOWN UNKNOWN or UNKNOWN = UNKNOWN Appendix B. Candidates for Future Protocol Extensions This Section summarizes issues which have been raised during the development of this specification, but for which no resolution could be found with the constraints in place. Future revisions of this specification should revisit these issues, though. B.1. Collation Support Matching and sorting of textual data relies on collations. With respect to WebDAV SEARCH, a combination of various design approaches could be used: o Require server support for specific collations. o Require that the server can advertise which collations it supports. Reschke, et al. Expires January 8, 2009 [Page 46]
Internet-Draft WebDAV SEARCH July 2008 o Allow a client to select the collation to be used. In practice, the current implementations of WebDAV SEARCH usually rely on backends they do not control, and for which collation information may not be available. To make things worse, implementations of the DAV:basicsearch grammar frequently need to combine data from multiple underlying stores (such as properties and full text content), and thus collation support may vary based on the operator or property. Another open issue is what collation formalism to support. At the time of this writing, the two specifications below seem to provide the necessary framework and thus may be the base for future work on collation support in WebDAV SEARCH: 1. "Internet Application Protocol Collation Registry" ([RFC4790]). 2. "XQuery 1.0 and XPath 2.0 Functions and Operators" ([XPATHFUNC], Section 7.3.1). B.2. Count DAV:basicsearch does not allow a request that returns the count of matching resources. A protocol extension would need to extend DAV:select, and also modify the DAV:multistatus response format. B.3. Diagnostics for Unsupported Queries There are many reasons why a given query may not be supported by a server. Query Schema Discovery (Section 4) can be used to discover some constraints, but not all. Future revisions should consider the introduction of specific condition codes ([RFC4918], Section 16) to these situations. B.4. Language Matching Section 5.12.2 defines language matching in terms of the XPath "lang" function ([XPATH], Section 4.3). Future revisions should consider building on [BCP47] instead. B.5. Matching Media Types Matching media types using the DAV:getcontenttype property and the DAV:like operator is hard due to DAV:getcontenttype also allowing parameters. A new operator specifically designed for the purpose of Reschke, et al. Expires January 8, 2009 [Page 47]
Internet-Draft WebDAV SEARCH July 2008 matching media types probably would simplify things a lot. See <http ://lists.w3.org/Archives/Public/www-webdav-dasl/2003OctDec/0109.html> for a specific proposal. B.6. Query by Name DAV:basicsearch operates on the properties (and optionally the contents) of resources, and thus doesn't really allow matching on parts of the resource's URI. See <http://lists.w3.org/Archives/ Public/www-webdav-dasl/2003OctDec/0100.html> for a proposed extension covering this use case. B.7. Result Paging A frequently discussed feature is the ability to specifically request the "next" set of results, when either the server decided to truncate the result, or the client explicitly asked for a limited set (for instance, using the DAV:limit element defined in Section 5.17). In this case, it would be desirable if the server could keep the full query result, and provide a new URI identifying a separate result resource, allowing the client to retrieve additional data through GET requests, and remove the result through a DELETE request. B.8. Search Scope Discovery Given a Search Arbiter resource, there's currently no way to discover programmatically the supported sets of search scopes. Future revisions of this specification could specify a scope discovery mechanism, similar to the Query Schema Discovery defined in Section 4. Appendix C. Change Log (to be removed by RFC Editor before publication) C.1. From draft-davis-dasl-protocol-xxx Feb 14, 1998 Initial Draft Feb 28, 1998 Referring to DASL as an extension to HTTP/1.1 rather than DAV. Added new sections "Notational Conventions", "Protocol Model", "Security Considerations". Changed section 3 to "Elements of Protocol". Added some stuff to introduction. Added "result set" terminology. Added "IANA Considerations". Reschke, et al. Expires January 8, 2009 [Page 48]
Internet-Draft WebDAV SEARCH July 2008 Mar 9, 1998 Moved sub-headings of "Elements of Protocol" to first level and removed "Elements of Protocol" Heading. Added an sentence in introduction explaining that this is a "sketch" of a protocol. Mar 11, 1998 Added orderby, data typing, three valued logic, query schema property, and element definitions for schema for basicsearch. April 8, 1998 - made changes based on last week's DASL BOF. May 8, 1998 Removed most of DAV:searcherror; converted to DAV: searchredirect Altered DAV:basicsearch grammar to use avoid use of ANY in DTD June 17, 1998 -Added details on Query Schema Discovery -Shortened list of data types June 23, 1998 moved data types before change history rewrote the data types section removed the casesensitive element and replace with the casesensitive attribute added the casesensitive attribute to the DTD for all operations that might work on a string Jul 20, 1998 A series of changes. See Author's meeting minutes for details. July 28, 1998 Changes as per author's meeting. QSD uses SEARCH, not PROPFIND. Moved text around to keep concepts nearby. Boolean literals are 1 and 0, not T and F. contains changed to contentspassthrough. Renamed rank to score. July 28, 1998 Added Dale Lowry as Author September 4, 1998 Added 422 as response when query lists unimplemented operators. DAV:literal declares a default value for xml:space, 'preserve' (see XML spec, section 2.10) moved to new XML namespace syntax September 22, 1998 Changed "simplesearch" to "basicsearch" Changed isnull to isdefined Defined NULLness as having a 404 or 403 response used ENTITY syntax in DTD Added redirect Reschke, et al. Expires January 8, 2009 [Page 49]
Internet-Draft WebDAV SEARCH July 2008 October 9, 1998 Fixed a series of typographical and formatting errors. Modified the section of three-valued logic to use a table rather than a text description of the role of UNKNOWN in expressions. November 2, 1998 Added the DAV:contains operator. Removed the DAV:contentpassthrough operator. November 18, 1998 Various author comments for submission June 3, 1999 Cosmetic and minor editorial changes only. Fix nits reported by Jim Whitehead in email of April 26, 1999. Converted to HTML from Word 97, manually. April 20, 2000 Removed redirection feature, since 301/302 suffices. Removed Query Schema Discovery (former chapter 4). Everyone agrees this is a useful feature, but it is apparently too difficult to define at this time, and it is not essential for DASL. C.2. since start of draft-reschke-webdav-search October 09, 2001 Added Julian Reschke as author. Chapter about QSD re-added. Formatted into RFC2629-compliant XML document. Added first comments. ID version number kicked up to draft-dasl-protocol-03. October 17, 2001 Updated address information for Jim Davis. Added issue of datatype vocabularies. Updated issue descriptions for grammar discovery, added issues on query schema DTD. Fixed typos in XML examples. December 17, 2001 Re-introduced split between normative and non- normative references. January 05, 2002 Version bumped up to 04. Started work on resolving the issues identified in the previous version. January 14, 2002 Fixed some XML typos. January 22, 2002 Closed issues naming-of-elements. Fixed query search DTD and added option to discover properties of "other" (non-listed) properties. Reschke, et al. Expires January 8, 2009 [Page 50]
Internet-Draft WebDAV SEARCH July 2008 January 25, 2002 Changed into private submission and added reference to historic DASL draft. Marked reference to DASL requirements non-normative. Updated reference to latest deltav spec. January 29, 2002 Added feedback from and updated contact info for Alan Babich. Included open issues collected in http://www.webdav.org/dasl/protocol/issues.html. February 8, 2002 Made sure that all artwork fits into 72 characters wide text. February 18, 2002 Changed Insufficient storage handling (multistatus). Moved is-collection to operators and added to DTD. Made scope/depth mandatory. February 20, 2002 Updated reference to SQL99. February 28, 2002 "Non-normative References" -> "Informative References". Abstract updated. Consistently specify a charset when using text/xml (no change bars). Do not attempt to define PROPFIND's entity encoding (take out specific references to text/ xml). Remove irrelevant headers (Connection:) from examples (no change bars). Added issue on querying based on DAV:href. Updated introduction to indicate relationship to DASL draft. Updated HTTP reference from RFC2068 to RFC2616. Updated XML reference to XML 1.0 2nd edition. March 1, 2002 Removed superfluous namespace decl in 2.4.2. Reopened JW14 and suggest to drop xml:space support. March 3, 2002 Removed "xml:space" feature on DAV:literal. Added issue about string comparison vs. collations vs. xml:lang. Updated some of the open issues with details from JimW's original mail in April 1999. Resolved scope vs relative URI references. Resolved issues about DAV:ascending (added to index) and the BNF for DAV:like (changed "octets" to "characters"). March 8, 2002 Updated reference to DeltaV (now RFC3253). Added Martin Wallmer's comments, moved JW5 into DAV:basicsearch section. March 11, 2002 Closed open issues regaring the type of search arbiters (JW3) and their discovery (JW9). Rephrased requirements on multistatus response bodies (propstat only if properties were selected, removed requirement for responsedescription). Reschke, et al. Expires January 8, 2009 [Page 51]
Internet-Draft WebDAV SEARCH July 2008 March 23, 2002 RFC2376 -> RFC3023. Added missing first names of authors. OPTIONS added to example for DAV:supported-method-set. C.3. since draft-reschke-webdav-search-00 March 29, 2002 Abstract doesn't refer to DASL WG anymore. April 7, 2002 Fixed section title (wrong property name supported- search-grammar-set. Changed DAV:casesensitve to "casesensitive" (it wasn't in the DAV: namespace after all). May 28, 2002 Updated some issues with Jim Davis's comments. June 10, 2002 Added proposal for different method for query schema discovery, not using pseudo-properties. June 25, 2002 QSD marshalling rewritten. Added issue "isdefined- optional". C.4. since draft-reschke-webdav-search-01 July 04, 2002 Added issue "scope-collection". July 08, 2002 Closed issue "scope-collection". August 12, 2002 Added issues "results-vs-binds" and "select- allprop". October 22, 2002 Added issue "undefined-expressions". November 18, 2002 Changed example host names (no change tracking). November 25, 2002 Updated issue "DB2/DB7". Closed issues "undefined expressions", "isdefined-optional" and "select-allprop". C.5. since draft-reschke-webdav-search-02 November 27, 2002 Added issues "undefined-properties", "like- exactlyone" and "like-wildcard-adjacent". Closed issue "query-on- href". Added acknowledgments section. November 28, 2002 Closed issue "like-exactlyone". Added issue "mixed-content-properties". December 14, 2002 Closed issues "undefined-properties", "results-vs- binds", "mixed-content-properties". Updated issue "like-wildcard- adjacent". Added informative reference to BIND draft. Updated reference to ACL draft. Reschke, et al. Expires January 8, 2009 [Page 52]
Internet-Draft WebDAV SEARCH July 2008 January 9, 2003 Removed duplicate section on invalid scopes. Added comments to some open issues. Closed issues JW25/26, score- pseudo-property and null-ordering. January 10, 2003 Issue limit-vs-ordering plus resolution. Closed issue JW17/JW24b. January 14, 2003 New issue order-precedence. Started resolution of DB2/DB7. January 15, 2003 Started spec of DAV:typed-literal. January 17, 2003 Fix one DAV:like/DAV:getcontenttype example (add / to like expression, make case-insensitive). January 28, 2003 Update issue(s) result-truncation, JW24d. Fixed response headers in OPTIONS example. Added issue qsd-optional. Closed issue(s) order-precedence, case-insensitivity-name. February 07, 2003 Added issue scope-vs-versions. score-pseudo- property: allow DAV:orderby to explicitly specify DAV:score. C.6. since draft-reschke-webdav-search-03 April 24, 2003 Fixed two "?" vs "_" issues (not updated in last draft). June 13, 2003 Improve index. C.7. since draft-reschke-webdav-search-04 July 7, 2003 Typo fixed (propstat without status element). August 11, 2003 Remove superfluous IP and copyright sections. September 09, 2003 Added issues "2.4-multiple-uris" and "5.1-name- filtering". October 06, 2003 Fix misplaced section end in 5.11, add table formatting. Enhance table formatting in 5.18.3. Updated ACL and BIND references. Added XPATH reference. Closed issue JW24d by adding new optional operators. Updated more open issues, added issues from January meeting. Add K. Wiggen to Acknowledgements. Add Contributors section for the authors of the original draft. Close issue "scope-vs-versions" (optional feature added). Close (new) issue "1.3-import-DTD-terminology". Add issue "1.3-import- requirements-terminology". Reschke, et al. Expires January 8, 2009 [Page 53]
Internet-Draft WebDAV SEARCH July 2008 October 07, 2003 Typos fixed. Moved statement about DAV: namespace usage into separate (sub-)section. Closed "1.3-import- requirements-terminology". Update I18N Considerations with new xml:lang support info (see issue JW24d). Close issue "DB2/DB7" (remaining typing issues are now summarized in issue "typed- literal"). Fix misplaced section end in section 7. Started change to use RFC3253-style method definitions and error marshalling. October 08, 2003 Remove obsolete language that allowed reporting invalid scopes and such inside multistatus. Add new issue "5.4.2- scope-vs-redirects". C.8. since draft-reschke-webdav-search-05 October 11, 2003 Separate DAV:basicsearch DTD into separate figures for better maintainability. Update DTD with language-* operators and typed-literal element (optional). October 14, 2003 Close issue "5.4.2-multiple-scope". November 04, 2003 Update reference from CaseMap to UNICODE4, section 5.18. November 16, 2003 Updated issue "5.1-name-filtering". November 24, 2003 Reformatted scope description (collection vs. non- collection). November 30, 2003 Add issue "5_media_type_match". February 6, 2004 Updated all references. C.9. since draft-reschke-webdav-search-06 July 05, 2004 Fix table in Appendix "Three-Valued Logic in DAV: basicsearch". September 14, 2004 Fix inconsistent DTD in section 5.2 and 5.4 for scope element. September 30, 2004 Rewrite editorial note and abstract. Update references (remove unneeded XMLNS, update ref to ACL and BIND specs). Reschke, et al. Expires January 8, 2009 [Page 54]
Internet-Draft WebDAV SEARCH July 2008 C.10. since draft-reschke-webdav-search-07 October 01, 2004 Fix previous section heading (no change tracking). October 13, 2004 Fix DTD entry for is-collection. November 1, 2004 Fix DTD fragment query-schema-discovery. December 11, 2004 Update BIND reference. January 01, 2005 Fix DASL and DASLREQ references. February 06, 2005 Update XS2 reference. February 11, 2005 Rewrite "like" and "DASL" (response header) grammar in ABNF. May 5, 2005 Update references. Close issue "abnf" (only use ABNF when applicable). C.11. since draft-reschke-webdav-search-08 May 06, 2005 Fix document title. September 25, 2005 Update BIND reference. October 05, 2005 Update RFC4234 reference. October 22, 2005 Author's address update. February 12, 2006 Update BIND reference. March 16, 2006 Add typed literals to QSD. August 20, 2006 Update XML reference. August 28, 2006 Add issues "5.3-select-count" (open) and "5.4- clarify-depth" (resolved). Update BIND reference (again). C.12. since draft-reschke-webdav-search-09 December 1, 2006 Fix ABNF for DASL header. December 16, 2006 Close issue "qsd-optional", leave QSD optional. Close issue "2.4-multiple-uris", suggesting that servers should only return one response element per resource in case of multiple bindings. Add and resolve issues "authentication" and "cleanup- iana" (adding the header registration for "DASL"). Re-write Reschke, et al. Expires January 8, 2009 [Page 55]
Internet-Draft WebDAV SEARCH July 2008 rational for using the DAV: namespace, although this is a non-WG submission. January 4, 2007 Close issue "JW16b/JW24a", being related to "language-comparison". Add Appendix B. Close issues "language- comparison", "5_media_type_match", "5.1-name-filtering" and "5.3- select-count" as "won't fix", and add appendices accordingly. January 24, 2007 Update BIND reference. Close issue "5.4.2-scope- vs-redirects". Close issue "typed-literal": specify in terms of the XPATH 2.9 casting mechanism. Close issue "1.3-apply- condition-code-terminology" (no changes). C.13. since draft-reschke-webdav-search-10 January 29, 2007 Issue "result-truncation": Add appendix describing the open issue of Result Paging. Describe the mechanism of marshalling truncated results in a new normative subsection (leave the actual example where it was). Add and resolve issues "rfc2606-compliance" and "response-format". Update contact information for Alan Babich, Jim Davis and Surendra Reddy (no change tracking). February 8, 2007 Update BIND reference. C.14. since draft-reschke-webdav-search-11 Update: draft-newman-i18n-comparator-14 is RFC4790. Update: RFC2518 replaced by draft-ietf-webdav-rfc2518bis. Updated BIND reference. Minor tweaks to intro (document organization and relation to DASL). C.15. since draft-reschke-webdav-search-12 Update: draft-ietf-webdav-rfc2518bis replaced by RFC4918. Updated BIND reference. C.16. since draft-reschke-webdav-search-13 Open and close issue "qsd-req-validity". Updated BIND reference. C.17. since draft-reschke-webdav-search-14 RFC4234 obsoleted by RFC5234. Add and resolve issues "5.19.8-opdesc-vs-contains" and "dtd". Add clarifications about the behaviour when literal values are not compatible with the type of a comparison. Reschke, et al. Expires January 8, 2009 [Page 56]
Internet-Draft WebDAV SEARCH July 2008 C.18. since draft-reschke-webdav-search-15 Minor editorial improvements. Fix description of DAV:scope/DAV:href to use proper URI terminology, add reference to RFC 3986. Clarify list nature of DASL header. Clarify that the DAV:like pattern ABNF is defined in terms of Unicode code points. Update to UNICODE5. Aim for standards track (affects introduction to Appendix B). Thus, make the dependency on [RFC4437] clearly optional, and make the reference informative. Also, mention BCP 47 as candidate for future changes to language matching. Mention definition of additional condition codes as candidate for future changes. Consider DAV:contains in Security Considerations. Update Surendra's and Alan's contact information. Mention search scope discovery as future extensions. Add a SHOULD level requirement for DAV:basicsearch search arbiters to support their own URI as search scope. Appendix D. Resolved issues (to be removed by RFC Editor before publication) Issues that were either rejected or resolved in this version of this document. D.1. standardstrack Type: change julian.reschke@greenbytes.de (2008-06-27): Umbrella issue for changes making this a candidate for the Standards Track. D.2. acls Type: edit Reschke, et al. Expires January 8, 2009 [Page 57]
Internet-Draft WebDAV SEARCH July 2008 julian.reschke@greenbytes.de (2008-06-29): Clarify security considerations with respect to access rights. D.3. scope-discovery Type: change julian.reschke@greenbytes.de (2008-07-02): State that there's no way to discover supported scopes, but also add a SHOULD requirement for a scope to be supported by DAV:basicsearch. D.4. 3.2-listsyntax In Section 3.2: Type: edit julian.reschke@greenbytes.de (2008-06-25): Clarify what HTTP-style list syntax in headers means; adjust examples. Resolution: Done. Appendix E. Open issues (to be removed by RFC Editor prior to publication) E.1. edit Type: edit julian.reschke@greenbytes.de (2004-07-05): Umbrella issue for editorial fixes/enhancements. Index C caseless attribute 28-29, 36 Condition Names DAV:search-grammar-discovery-supported (pre) 10 DAV:search-grammar-supported (pre) 10 DAV:search-multiple-scope-supported (pre) 10 DAV:search-scope-valid (pre) 11 Criteria 6 D DAV:and 28 DAV:ascending 28 Reschke, et al. Expires January 8, 2009 [Page 58]
Internet-Draft WebDAV SEARCH July 2008 DAV:contains 33 DAV:depth 25 DAV:descending 28 DAV:eq 29 caseless attribute 29 DAV:from 25 DAV:gt 29 DAV:gte 29 DAV:include-versions 25 DAV:is-collection 31 DAV:is-defined 32 DAV:language-defined 31 DAV:language-matches 31 DAV:like 32 DAV:limit 35 DAV:literal 29 DAV:lt 29 DAV:lte 29 DAV:not 28 DAV:nresults 35 DAV:or 28 DAV:orderby 28 DAV:scope 25 DAV:score 34 relationship to DAV:orderby 35 DAV:search-grammar-discovery-supported precondition 10 DAV:search-grammar-supported precondition 10 DAV:search-multiple-scope-supported precondition 10 DAV:search-scope-valid precondition 11 DAV:select 25 DAV:supported-query-grammar-set property 16 DAV:typed-literal 29 DAV:where 26 M Methods SEARCH 9 O OPTIONS method 15 DASL response header 16 P Properties DAV:supported-query-grammar-set 16 Q Query 6 Reschke, et al. Expires January 8, 2009 [Page 59]
Internet-Draft WebDAV SEARCH July 2008 Query Grammar 7 Query Grammar Discovery 15 using live property 16 using OPTIONS 15 Query Schema 7 R Result 7 Result Record 7 Result Record Definition 7 Result Set 7 Result Set Truncation Example 11 S Scope 7 Search Arbiter 7 SEARCH method 9 Search Modifier 7 Sort Specification 8 Authors' Addresses Julian F. Reschke (editor) greenbytes GmbH Hafenweg 16 Muenster, NW 48155 Germany Phone: +49 251 2807760 Email: julian.reschke@greenbytes.de URI: http://greenbytes.de/tech/webdav/ Surendra Reddy Mitrix, Inc. 303 Twin Dolphin Drive, Suite 600-37 Redwood City, CA 94065 U.S.A. Phone: +1 408 500 1135 Email: Surendra.Reddy@mitrix.com Reschke, et al. Expires January 8, 2009 [Page 60]
Internet-Draft WebDAV SEARCH July 2008 Jim Davis 27 Borden Street Toronto, Ontario M5S 2M8 Canada Phone: +1 416 929 5854 Email: jrd3@alum.mit.edu URI: http://www.econetwork.net/~jdavis Alan Babich IBM Corporation 3565 Harbor Blvd. Costa Mesa, CA 92626 U.S.A. Phone: +1 714 327 3403 Email: ababich@us.ibm.com Reschke, et al. Expires January 8, 2009 [Page 61]
Internet-Draft WebDAV SEARCH July 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Reschke, et al. Expires January 8, 2009 [Page 62]