Network Working Group J. F. Reschke
Internet Draft greenbytes
Expires: May 2003 S. Reddy
Oracle
J. Davis
Intelligent Markets
A. Babich
Filenet
November 2002
WebDAV SEARCH
draft-reschke-webdav-search-02
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. 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
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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
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This Internet-Draft will expire in May 2003.
Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
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
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Internet Draft WebDAV SEARCH November 2002
client-supplied criteria.
Distribution of this document is unlimited. Please send comments to
the Distributed Authoring and Versioning (WebDAV) DASL mailing list
at www-webdav-dasl@w3.org, which may be joined by sending a message
with subject "subscribe" to www-webdav-dasl-request@w3.org.
Discussions of the WebDAV DASL mailing list are archived at URL:
http://www.w3.org/pub/WWW/Archives/Public/www-webdav-dasl/.
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Table of Contents
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Table of Contents . . . . . . . . . . . . . . . . . . . . . . 3
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1 DASL . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2 Relationship to DAV . . . . . . . . . . . . . . . . . . 5
1.3 Terms . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.4 Notational Conventions . . . . . . . . . . . . . . . . . 6
1.5 An Overview of DASL at Work . . . . . . . . . . . . . . 6
2 The SEARCH Method . . . . . . . . . . . . . . . . . . . . . 7
2.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 The Request . . . . . . . . . . . . . . . . . . . . . . 7
2.2.1 The Request-URI . . . . . . . . . . . . . . . . . . 7
2.2.2 The Request Body . . . . . . . . . . . . . . . . . . 7
2.3 The DAV:searchrequest XML Element . . . . . . . . . . . 8
2.4 The Successful 207 (Multistatus) Response . . . . . . . 8
2.4.1 Extending the PROPFIND Response . . . . . . . . . . 8
2.4.2 Example: A Simple Request and Response . . . . . . . 8
2.4.3 Example: Result Set Truncation . . . . . . . . . . . 9
2.5 Unsuccessful Responses . . . . . . . . . . . . . . . . . 11
2.6 Invalid Scopes . . . . . . . . . . . . . . . . . . . . . 11
2.6.1 Indicating an Invalid Scope . . . . . . . . . . . . 11
2.6.2 Example of an Invalid Scope . . . . . . . . . . . . 12
3 Discovery of Supported Query Grammars . . . . . . . . . . . 13
3.1 The OPTIONS Method . . . . . . . . . . . . . . . . . . . 13
3.2 The DASL Response Header . . . . . . . . . . . . . . . . 13
3.3 DAV:supported-query-grammar-set (protected) . . . . . . 14
3.4 Example: Grammar Discovery . . . . . . . . . . . . . . . 14
4 Query Schema Discovery: QSD . . . . . . . . . . . . . . . . 17
4.1 Additional SEARCH semantics . . . . . . . . . . . . . . 17
4.1.1 Example of query schema discovery . . . . . . . . . 18
5 The DAV:basicsearch Grammar . . . . . . . . . . . . . . . . 20
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . 20
5.2 The DAV:basicsearch DTD . . . . . . . . . . . . . . . . 20
5.2.1 Example Query . . . . . . . . . . . . . . . . . . . 21
5.3 DAV:select . . . . . . . . . . . . . . . . . . . . . . . 22
5.4 DAV:from . . . . . . . . . . . . . . . . . . . . . . . . 22
5.4.1 Relationship to the Request-URI . . . . . . . . . . 23
5.4.2 Scope . . . . . . . . . . . . . . . . . . . . . . . 23
5.5 DAV:where . . . . . . . . . . . . . . . . . . . . . . . 24
5.5.1 Use of Three-Valued Logic in Queries . . . . . . . . 24
5.5.2 Handling Optional operators . . . . . . . . . . . . 24
5.5.3 Treatment of NULL Values . . . . . . . . . . . . . . 24
5.5.4 Treatment of properties with mixed/element content . 25
5.5.5 Example: Testing for Equality . . . . . . . . . . . 25
5.5.6 Example: Relative Comparisons . . . . . . . . . . . 25
5.6 DAV:orderby . . . . . . . . . . . . . . . . . . . . . . 26
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5.6.1 Comparing Natural Language Strings. . . . . . . . . 26
5.6.2 Example of Sorting . . . . . . . . . . . . . . . . . 26
5.7 Boolean Operators: DAV:and, DAV:or, and DAV:not . . . . 27
5.8 DAV:eq . . . . . . . . . . . . . . . . . . . . . . . . . 27
5.9 DAV:lt, DAV:lte, DAV:gt, DAV:gte . . . . . . . . . . . . 27
5.10 DAV:literal . . . . . . . . . . . . . . . . . . . . . . 27
5.11 DAV:is-collection . . . . . . . . . . . . . . . . . . . 28
5.11.1 Example of DAV:is-collection . . . . . . . . . . . 28
5.12 DAV:isdefined . . . . . . . . . . . . . . . . . . . . . 28
5.13 DAV:like . . . . . . . . . . . . . . . . . . . . . . . 29
5.13.1 Syntax for the Literal Pattern . . . . . . . . . . 29
5.13.2 Example of DAV:like . . . . . . . . . . . . . . . . 29
5.14 DAV:contains . . . . . . . . . . . . . . . . . . . . . 30
5.14.1 Examples . . . . . . . . . . . . . . . . . . . . . 30
5.15 The DAV:limit XML Element . . . . . . . . . . . . . . . 31
5.16 The DAV:nresults XML Element . . . . . . . . . . . . . 31
5.17 The "casesensitive" XML attribute . . . . . . . . . . . 32
5.18 The DAV:score Property . . . . . . . . . . . . . . . . 32
5.19 Query schema for DAV:basicsearch . . . . . . . . . . . 33
5.19.1 DTD for DAV:basicsearch QSD . . . . . . . . . . . . 33
5.19.2 DAV:propdesc Element . . . . . . . . . . . . . . . 33
5.19.2.1 DAV:any-other-property . . . . . . . . . . . . 34
5.19.3 The DAV:datatype Property Description . . . . . . . 34
5.19.4 The DAV:searchable Property Description . . . . . . 35
5.19.5 The DAV:selectable Property Description . . . . . . 35
5.19.6 The DAV:sortable Property Description . . . . . . . 35
5.19.7 The DAV:casesensitive Property Description . . . . 36
5.19.8 The DAV:operators XML Element . . . . . . . . . . . 36
5.19.9 Example of Query Schema for DAV:basicsearch . . . . 36
6 Internationalization Considerations . . . . . . . . . . . . 38
7 Security Considerations . . . . . . . . . . . . . . . . . . 39
8 Scalability . . . . . . . . . . . . . . . . . . . . . . . . 40
9 Authentication . . . . . . . . . . . . . . . . . . . . . . . 41
10 IANA Considerations . . . . . . . . . . . . . . . . . . . . 42
11 Copyright . . . . . . . . . . . . . . . . . . . . . . . . . 43
12 Intellectual Property . . . . . . . . . . . . . . . . . . . 44
Normative References . . . . . . . . . . . . . . . . . . . . . 45
Informative References . . . . . . . . . . . . . . . . . . . . 45
Author's Addresses . . . . . . . . . . . . . . . . . . . . . . 46
A Three-Valued Logic in DAV:basicsearch . . . . . . . . . . . 47
B Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 49
B.1 From draft-davis-dasl-protocol-xxx . . . . . . . . . . . 49
B.2 since start of draft-reschke-webdav-search . . . . . . . 50
B.3 since draft-reschke-webdav-search-00 . . . . . . . . . . 52
B.4 since draft-reschke-webdav-search-01 . . . . . . . . . . 52
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
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1 Introduction
1.1 DASL
This document defines WebDAV SEARCH, an application of HTTP/1.1
forming a lightweight search protocol to transport queries and result
sets and allows clients to make use of server-side search facilities.
It is based on the expired draft for WebDAV DASL [DASL]. [DASLREQ]
describes the motivation for DASL.
DASL will minimize 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,
o the DASL response header,
o the DAV:searchrequest XML element,
o the DAV:queryschema property,
o the DAV:basicsearch XML element and query grammar, and
o the DAV:basicsearchschema XML element.
For WebDAV-compliant servers, it also defines a new live property
DAV:supported-query-grammar-set.
1.2 Relationship to DAV
DASL relies on the resource and property model defined by [RFC2518].
DASL does not alter this model. Instead, DASL allows clients to
access DAV-modeled resources through server-side search.
1.3 Terms
This draft uses the terms defined in [RFC2616], [RFC2518], and
[DASLREQ].
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1.4 Notational Conventions
The augmented BNF used by this document to describe protocol elements
is exactly the same as the one described in Section 2.1 of [RFC2616].
Because this augmented BNF uses the basic production rules provided
in Section 2.2 of [RFC2616], those rules apply to this document as
well.
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].
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.
Note that this draft currently defines elements and properties in the
WebDAV namespace "DAV:", which it shouldn't do as it isn't a work
item of the WebDAV working group. The reason for this is the desire
for some kind of backward compatibility to the expired DASL drafts
and the assumption that the draft may become an official RFC
submission of the WebDAV working group at a later point of time.
Similarily, 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.
1.5 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 [RFC2518] PROPFIND response.
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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 [RFC2518] PROPFIND response.
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.
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 [RFC2518]), 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, the FOO 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.
If the client sends a text/xml or application/xml body, it MUST
include the DAV:searchrequest XML element. The DAV:searchrequest XML
element identifies the query grammar, defines the criteria, the
result record, and any other details needed to perform the search.
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2.3 The DAV:searchrequest XML Element
<!ELEMENT searchrequest ANY >
The DAV:searchrequest XML element contains a single XML element that
defines the query. The name of the query element defines the type of
the query. The value of that element defines the query itself.
2.4 The Successful 207 (Multistatus) Response
If the server returns 207 (Multistatus), then the search proceeded
successfully and the response MUST match that of a PROPFIND. 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.
In addition, the server MAY include DAV:response items in the reply
where the DAV:href element contains a URI that is not a matching
resource, e.g. that of a scope or the query arbiter. Each such
response item MUST NOT contain a DAV:propstat element, and MUST
contain a DAV:status element (unless no property was selected).
2.4.1 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.
2.4.2 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
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selected resource.
>> Request:
SEARCH / HTTP/1.1
Host: example.org
Content-Type: application/xml
Content-Length: xxx
<?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>
>> Response:
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="UTF-8"?>
<D:multistatus xmlns:D="DAV:"
xmlns:R="http://example.org/propschema">
<D:response>
<D:href>http://siamiam.test/</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:propstat>
</D:response>
</D:multistatus>
2.4.3 Example: 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
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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.
>> Request:
SEARCH / HTTP/1.1
Host: example.net
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
... the query goes here ...
>> Response:
HTTP/1.1 207 Multistatus
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?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:propstat>
<D:prop/>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>http://tech.mit.test/archive96/photos/Lesh1.jpg</D:href>
<D:propstat>
<D:prop/>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
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<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>
2.5 Unsuccessful Responses
If an error occurred that prevented execution of the query, the
server MUST indicate the failure with the appropriate status code and
SHOULD include a DAV:multistatus element to point out errors
associated with scopes.
400 Bad Request. The query could not be executed. The request may be
malformed (not valid XML for example). Additionally, this can be used
for invalid scopes and search redirections.
422 Unprocessable entity. The query could not be executed. If a
application/xml or text/xml request entity was provided, then it may
have been well-formed but may have contained an unsupported or
unimplemented query operator.
2.6 Invalid Scopes
2.6.1 Indicating an Invalid Scope
A client may submit a scope that the arbiter may be unable to query.
The inability to query may be due to network failure, administrative
policy, security, etc. This raises the condition described as an
"invalid scope".
To indicate an invalid scope, the server MUST respond with a 400 (Bad
Request).
The response includes a body with a DAV:multistatus element. Each
DAV:response in the DAV:multistatus identifies a scope. To indicate
that this scope is the source of the error, the server MUST include
the DAV:scopeerror element.
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2.6.2 Example of an Invalid Scope
>> Response:
HTTP/1.1 400 Bad-Request
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="UTF-8"?>
<d:multistatus xmlns:d="DAV:">
<d:response>
<d:href>http://www.example.com/X</d:href>
<d:status>HTTP/1.1 404 Object Not Found</d:status>
<d:scopeerror/>
</d:response>
</d:multistatus>
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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 [ACL] 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 defined in
[RFC2616].
If a resource supports the SEARCH method, then the server MUST list
SEARCH in the OPTIONS response as defined by [RFC2616].
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
>> Response:
DASLHeader = "DASL" ":" Coded-URL-List
Coded-URL-List : Coded-URL [ "," Coded-URL-List ]
Coded-URL ; defined in section 9.4 of [RFC2518]
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The DASL response header indicates server support for a query grammar
in the OPTIONS method. The value is a URI that indicates the type of
grammar. Note that although the URI 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 it's namespace name (a URI reference) and the element's
local name).
This header MAY be repeated.
For example:
DASL: <http://foobar.test/syntax1>
DASL: <http://akuma.test/syntax2>
DASL: <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 [ACL] 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.test/syntax1 and http://akuma.test/syntax2. Note that
every server MUST support DAV:basicsearch.
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>> Request:
OPTIONS /somefolder HTTP/1.1
Host: example.org
>> Response:
HTTP/1.1 200 OK
Date: Tue, 20 Jan 1998 20:52:29 GMT
Allow: OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE, COPY, MOVE,
MKCOL, PROPFIND, PROPPATCH, LOCK, UNLOCK, SEARCH
DASL: <DAV:basicsearch>
DASL: <http://foobar.test/syntax1>
DASL: <http://akuma.test/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: xxx
<?xml version="1.0" encoding="UTF-8" ?>
<propfind xmlns="DAV:">
<prop>
<supported-query-grammar-set/>
<supported-method-set/>
</prop>
</propfind>
>> Response:
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
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Content-Length: xxx
<?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.test" /></grammar>
</supported-query-grammar>
<supported-query-grammar>
<grammar><syntax2 xmlns="http://akuma.test/"/></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
in an XML based query.
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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 a 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 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
scope and with a root element of DAV:query-schema-discovery rather
than DAV:searchrequest.
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Marshalling:
The requst body MUST be DAV:query-schema-discovery element.
<!ELEMENT query-schema-discovery ANY>
ANY value: XML element defining a valid query
The response body takes the form of a RFC2518 DAV:multistatus
element, where DAV:response is extended to hold the returned query
grammar inside a DAV:query-schema container element.
<!ELEMENT response (href, ((href*, status)|(propstat+)),
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.test, the grammar is
DAV:basicsearch, the scope is also recipes.test.
>> Request:
SEARCH / HTTP/1.1
Host: recipes.test
Content-Type: application/xml
Content-Length: xxx
<?xml version="1.0"?>
<query-schema-discovery xmlns="DAV:">
<basicsearch>
<from>
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<scope>
<href>http://recipes.test</href>
<depth>infinity</depth>
</scope>
</from>
</basicsearch>
</query-schema-discovery>
>> Response:
HTTP/1.1 207 Multistatus
Content-Type: application/xml
Content-Length: xxx
<?xml version="1.0"?>
<multistatus xmlns="DAV:">
<response>
<href>http://recipes.test</href>
<status>HTTP/1.1 200 OK</status>
<query-schema>
<basicsearchschema>
(See section "Query schema for DAV:basicsearch" for
the actual contents)
</basicsearchschema>
</query-schema>
</response>
</multistatus>
The query schema for DAV:basicsearch is defined in Section 5.19.
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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 others 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.
5.2 The DAV:basicsearch DTD
<!ELEMENT basicsearch (select, from, where?, orderby?, limit?) >
<!ELEMENT select (allprop | prop) >
<!ELEMENT from (scope) >
<!ELEMENT scope (href, depth) >
<!ENTITY %comp_ops "eq | lt | gt| lte | gte">
<!ENTITY %log_ops "and | or | not">
<!ENTITY %special_ops "is-collection | isdefined">
<!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; ) >
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<!ELEMENT and ( ( %all_ops; ) +) >
<!ELEMENT or ( ( %all_ops; ) +) >
<!ELEMENT not ( %all_ops; ) >
<!ELEMENT lt ( prop , literal ) >
<!ATTLIST lt casesensitive (1|0) "1" >
<!ELEMENT lte ( prop , literal ) >
<!ATTLIST lte casesensitive (1|0) "1" >
<!ELEMENT gt ( prop , literal) >
<!ATTLIST gt casesensitive (1|0) "1" >
<!ELEMENT gte ( prop , literal ) >
<!ATTLIST gte casesensitive (1|0) "1" >
<!ELEMENT eq ( prop , literal ) >
<!ATTLIST eq casesensitive (1|0) "1" >
<!ELEMENT literal (#PCDATA)>
<!ELEMENT isdefined (prop) >
<!ELEMENT like (prop, literal) >
<!ATTLIST like casesensitive (1|0) "1" >
<!ELEMENT contains (#PCDATA)>
<!ELEMENT orderby (order+) >
<!ELEMENT order (prop, (ascending | descending)?)
<!ATTLIST order casesensitive (1|0) "1" >
<!ELEMENT ascending EMPTY>
<!ELEMENT descending EMPTY>
<!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
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exceeds 10000.
<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>
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 [RFC2518]and revised in [RFC3253].
5.4 DAV:from
DAV:from defines the query scope. This contains exactly one DAV:scope
element. The scope element contains mandatory DAV:href and DAV:depth
elements.
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DAV:href indicates the URI 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
(toplevel) members of the collection. When it is "infinity", the
search includes all recursive members of the collection.
5.4.1 Relationship to the Request-URI
If the DAV:scope element is an absolute URI, the scope is exactly
that URI.
If the DAV:scope element is is an absolute URI reference, the scope
is taken to be relative to the request-URI.
5.4.2 Scope
A Scope can be an arbitrary URI.
Servers, of course, may support only particular scopes. This may
include limitations for particular schemes such as "http:" or "ftp:"
or certain URI namespaces.
If a scope is given that is not supported the server MUST respond
with a 400 status code that includes a Multistatus error. A scope in
the query appears as a resource in the response and must include an
appropriate status code indicating its validity with respect to the
search arbiter.
Example:
HTTP/1.1 400 Bad Request
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="UTF-8"?>
<d:multistatus xmlns:d="DAV:">
<d:response>
<d:href>http://www.example.com/scope1</d:href>
<d:status>HTTP/1.1 502 Bad Gateway</d:status>
</d:response>
</d:multistatus>
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This example shows the response if there is a scope error. The
response provides a Multistatus with a status for the scope. In this
case, the scope cannot be reached because the server cannot search
another server (502).
5.5 DAV:where
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 Section 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 404 or 403 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:isdefined operator is defined to test if the value of a
property is NULL.
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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 DAV:basicsearch. For querying the
DAV:resourcetype property, see Section 5.11.
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 that are "image/gifs"
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>
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<D:literal>4096</D:literal>
</D:gt>
</D:and>
</D:where>
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 ( as in [SQL99]).
5.6.1 Comparing Natural Language Strings.
Comparisons on strings take into account the language defined for
that property. Clients MAY specify the language using the xml:lang
attribute. If no language is specified either by the client or
defined for that property by the server or if a comparison is
performed on strings of two different languages, the results are
undefined.
The "casesensitive" attribute may be used to indicate case-
sensitivity for comparisons. Servers SHOULD do caseless matching as
defined in [CaseMap].
5.6.2 Example of Sorting
This sort orders first by last name of the author, and then by size,
in descending order, so that the largest works appear first.
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<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
it contains.
5.8 DAV:eq
The DAV:eq operator provides simple equality matching on property
values.
The "casesensitive" attribute may be used with this element.
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
"casesensitive" attribute may be used with these elements.
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 [RFC2518], clients SHOULD NOT specify the attribute
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"xml:space" (section 2.10 of [XML]) to override this behaviour.
5.11 DAV:is-collection
The DAV:is-collection operator allows clients to determine whether a
resource is a collection (that is, whether it's DAV:resourcetype
element contains the element DAV:collection).
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.
5.11.1 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>
5.12 DAV:isdefined
The DAV:isdefined 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:isdefined>
<d:prop><x:someprop/></d:prop>
</d:isdefined>
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5.13 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.
5.13.1 Syntax for the Literal Pattern
Pattern := [wildcard] 0*( text [wildcard] )
wildcard := exactlyone | zeroormore
text := 1*( <character> | escapesequence )
exactlyone : = "?"
zeroormore := "%"
escapechar := "\"
escapesequence := "\" ( exactlyone | zeroormore | escapechar )
character: see section 2.2 of [XML]
The value for the literal is composed of wildcards separated by
segments of text. Wildcards may begin or end the literal. Wildcards
may not be adjacent.
The "?" wildcard matches exactly one character.
The "%" wildcard matches zero or more characters
The "
5.13.2 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.
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<D:where>
<D:like>
<D:prop><D:getcontenttype/></D:prop>
<D:literal>image%</D:literal>
</D:like>
</D:where>
5.14 DAV:contains
The DAV:contains operator is an optional operator that provides
content-based search capability. This operator implicitly searches
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 left to the
server.
The following things 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.
The DAV:score property is intended to be useful to rank documents
satisfying the DAV:contains operator.
5.14.1 Examples
The example below shows a search for the phrase "Peter Forsberg".
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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>
5.15 The DAV:limit XML Element
<!ELEMENT limit (nresults) >
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.
5.16 The DAV:nresults XML Element
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<!ELEMENT nresults (#PCDATA)> ;only digits
The DAV:nresults XML element contains a requested maximum number of
records to be returned in a reply. The server MAY disregard this
limit. The value of this element is an integer.
5.17 The "casesensitive" XML attribute
The "casesensitive" attribute allows clients to specify case-
sensitive or case-insensitive behavior for DAV:basicsearch operators.
The possible values for "casesensitive" are "1" or "0". The "1" value
indicates case-sensitivity. The "0" value indicates case-
insensitivity. The default value is server-specified. Case-
insensitivity SHOULD implemented using caseless matching as defined
in [CaseMap].
Support for the "casesensitive" attribute is optional. A server
should respond with a status of 422 if it is used but cannot be
supported.
5.18 The DAV:score Property
<!ELEMENT score (#PCDATA)>
The DAV:score XML element is a synthetic property whose value is
defined only in the context of a query result where the server
computes a score, e.g. based on relevance. It may be used in
DAV:select or DAV:orderby elements. Servers SHOULD support this
property. 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).
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.
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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?,
casesensitive?)>
<!ELEMENT operators (opdesc*)>
<!ELEMENT opdesc ANY>
<!ELEMENT operand-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.
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
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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:casesensitive)
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. Datatypes
are identified by an element name. Where appropriate, a server SHOULD
use the simple datatypes 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
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xs:float .314159265358979E+1
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>
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5.19.7 The DAV:casesensitive 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 case sensitive. (The default is case insensitive.)
<!ELEMENT casesensitive 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. The
listing for an operator consists of the operator (as an empty
element), followed by one element for each operand. The operand MUST
be either DAV:operand-property or DAV:operand-literal, which indicate
that the operand in the corresponding position is a property or a
literal value, respectively. If an operator is polymorphic (allows
more than one operand syntax) then each permitted syntax MUST be
listed separately.
<operators xmlns='DAV:'>
<opdesc>
<like/><operand-property/><operand-literal/>
</opdesc>
</operators>
5.19.9 Example of Query Schema for DAV:basicsearch
<D:basicsearchschema xmlns:D="DAV:"
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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:operators>
</D:basicsearchschema>
This response lists four properties. The datatype 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:isdefined and
DAV:like are supported.
Note: The schema discovery defined here does not provide for
discovery of supported values of the "casesensitive" attribute. This
may require that the reply also list the mandatory operators.
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6 Internationalization Considerations
Clients have the opportunity to tag properties when they are stored
in a language. The server SHOULD read this language-tagging by
examining the xml:lang attribute on any properties stored on a
resource.
The xml:lang attribute specifies a nationalized collation sequence
when properties are compared.
Comparisons when this attribute differs have undefined order.
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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 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 one to retrieve information about values or
existence of properties that one could not obtain via PROPFIND. (e.g.
by use in DAV:orderby, or in expressions on properties.)
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
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.
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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://")
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9 Authentication
Authentication mechanisms defined in WebDAV will also apply to DASL.
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10 IANA Considerations
This document uses the namespace defined by [RFC2518] for XML
elements. All other IANA considerations mentioned in [RFC2518] are
also applicable to DASL.
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11 Copyright
To be supplied.
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12 Intellectual Property
To be supplied.
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Normative References
[ACL] Clemm, G., Hopkins, A., Sedlar, E. and Whitehead, J.,
"WebDAV Access Control Protocol", ID draft-ietf-webdav-
acl-07, November 2001.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2518] Goland, Y., Whitehead, E., Faizi, A., Carter, S.R. and
Jensen, D., "HTTP Extensions for Distributed Authoring --
WEBDAV", RFC 2518, February 1999.
[RFC2616] Fielding, R.T., Gettys, J., Mogul, J.C., Nielsen, H.F.,
Masinter, L., Leach, P.J. and Berners-Lee, T., "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC3023] Makoto, M., St.Laurent, S. and Kohn, D., "XML Media
Types", RFC 3023, January 2001.
[RFC3253] Clemm, G., Amsden, J., Ellison, T., Kaler, C. and
Whitehead, J., "Versioning Extensions to WebDAV", RFC
3253, March 2002.
[XML] Bray, T., Paoli, J., Sperberg-McQueen, C.M. and Maler, E.,
"Extensible Markup Language (XML) 1.0 (2nd ed)", W3C REC-
xml, October 2000.
[XMLNS] Bray, T., Hollander, D. and Layman, A., "Namespaces in
XML", W3C REC-xml-names, January 1999.
[XS2] Biron, P. V., Malhotra, A. and World Wide Web Consortium,
"XML Schema Part 2: Datatypes", W3C XS2, May 2001.
Informative References
[CaseMap] Davis, M., "Case Mappings", Unicode Techical Reports 21,
February 2001.
[DASL] Reddy, S., Lowry, D., Reddy, S., Henderson, R., Davis, J.
and Babich, A., "DAV Searching & Locating", ID draft-dasl-
protocol-00, July 1999.
[DASLREQ] Davis, J., Reddy, S. and Slein, J., "Requirements for DAV
Searching and Locating", ID draft-dasl-requirements-01,
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February 1999.
[SQL99] Milton, J., "Database Language SQL Part 2: Foundation
(SQL/Foundation)", ISO ISO/IEC 9075-2:1999 (E), July 1999.
Author's Addresses
Julian F. Reschke
greenbytes GmbH
Salzmannstrasse 152
Muenster, NW 48159
Germany
Phone: +49 251 2807760
Fax: +49 251 2807761
EMail: julian.reschke@greenbytes.de
URI: http://greenbytes.de/tech/webdav/
Surendra Reddy
Oracle Corporation
600 Oracle Parkway, M/S 6op3
Redwoodshores, CA 94065
Phone: +1 650 506 5441
EMail: Surendra.Reddy@oracle.com
Jim Davis
Intelligent Markets
410 Jessie Street 6th floor
San Francisco, CA 94103
EMail: jrd3@alum.mit.edu
Alan Babich
FileNET Corp.
3565 Harbor Blvd.
Costa Mesa, CA 92626
Phone: +1 714 327 3403
EMail: ababich@filenet.com
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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
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:
UNKNOWN and UNKNOWN = UNKNOWN
UNKNOWN or UNKKNOWN = UNKNOWN
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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
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B Change Log
B.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".
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.
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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
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.
B.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.
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January 05, 2002 Version bumbed 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.
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
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(propstat only if properties were selected, removed
requirement for responsedescription).
March 23, 2002 RFC2376 -> RFC3023. Added missing first names of
authors. OPTIONS added to example for
DAV:supported-method-set.
B.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".
B.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".
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Index
D S
DAV:ascending Scope
XML element 5.6 Invalid 2.6
DAV:descending SEARCH method
XML element 5.6 2
DAV:searchrequest
XML element 2.3
DAV:supported-query-grammar-set
property 3.3
O
OPTIONS method
3.1DASL response header
3.2
Q
Query Grammar Discovery
3using OPTIONS 3.1
using live property 3.3
R
Result Set Truncation
Example 2.4.3
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Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved.
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explain it or assist in its implementation may be prepared,
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Acknowledgement
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