X.500 URI Attribute Types and Object Class Mark Smith
INTERNET-DRAFT University of Michigan
11 October 1995
Definition of X.500 Attribute Types and an Object Class to Hold
Uniform Resource Identifiers (URIs)
Filename: draft-ietf-asid-x500-url-02.txt
Status of this Memo
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This Internet Draft expires April 11, 1995.
Abstract
Uniform Resource Locators (URLs) are being widely used to specify the
location of Internet resources. There is an urgent need to be able
to include URLs in the X.500 directory, and a desire to include other
types of Uniform Resource Identifiers (URIs) as they are defined. A
number of independent groups are already experimenting with the
inclusion of URLs in the X.500 directory. This document builds on
the experimentation to date and defines two new attribute types and
an auxiliary object class to allow URIs, including URLs, to be stored
in directory entries in a standard way.
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Background and Intended Usage
Uniform Resource Locators (URLs) as defined by [1] are the first of
several types of Uniform Resource Identifiers (URIs) being defined by
the IETF. This document defines two X.500 [2,3] attribute types
(labeledURI and labeledURL) and an auxiliary object class
(labeledURIObject) to hold all types of URIs, including URLs. It is
assumed that as other kinds of URIs are defined, additional attribute
types may be created to support storing them in directory entries.
The rationale for adding separate attribute types for the different
kinds of URIs is to support efficient programmatic access to specific
types of URIs. For example, if an indexing service is only
interested in URLs, having them available in their own attribute
makes pulling them out of a directory entry straightforward and
efficient.
It is intended that the schema elements defined in this document will
be progressed according to the process defined by the Internet X.500
Schema Working Group [4].
Schema Definition of the labeledURL Attribute Type
Name: labeledURL
ShortName: None
Description: Uniform Resource Locator with optional label
OID: umichAttributeType.41 (1.3.6.1.4.1.250.1.41)
Syntax: caseExactString
SizeRestriction: None
SingleValued: False
Discussion of the labeledURL Attribute Type
The labeledURL attribute type has the caseExactString syntax (since
URLs are case-sensitive) and it is multivalued. Values placed in the
attribute should consist of a URL as defined in [1] optionally
followed by one or more space characters and a label. Since space
characters are not allowed to appear un-encoded in URLs, there is no
ambiguity about where the label begins. Multiple labeledURL values
will generally indicate different resources that are all related to
the X.500 object, but may indicate different locations for the same
resource.
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The label is used to describe the resource to which the URL points,
and is intended as a friendly name fit for human consumption. This
document does not propose any specific syntax for the label part.
Note that in some cases it may be helpful to include in the label
some indication of the kind and/or size of the resource referenced by
the URL.
Note that the label may include any characters allowed by the
caseExactString syntax, but that the use of non-IA5 (non-ASCII)
characters is discouraged as not all directory clients may handle
them in the same manner.
Some examples of valid labeledURL values (the first does not have a
label):
ftp://ds.internic.net/rfc/rfc822.txt
http://www.umich.edu/ University of Michigan Home Page
http://champagne.inria.fr/Unites/rennes.gif Rennes [photo]
Schema Definition of the labeledURI Attribute Type
Name: labeledURI
ShortName: None
Description: Uniform Resource Identifier with optional label
OID: umichAttributeType.57 (1.3.6.1.4.1.250.1.57)
Syntax: caseExactString
SizeRestriction: None
SingleValued: False
Discussion of the labeledURI Attribute Type
The labeledURI attribute type has the caseExactString syntax (since
URIs are case-sensitive) and it is multivalued. Values placed in the
attribute should consist of a URI (at the present time, a URL)
optionally followed by one or more space characters and a label.
Since space characters are not allowed to appear un-encoded in URIs,
there is no ambiguity about where the label begins. At the present
time, the URI portion must comply with the URL specification [1].
Multiple labeledURI values will generally indicate different
resources that are all related to the X.500 object, but may indicate
different locations for the same resource.
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The label is used to describe the resource to which the URI points,
and is intended as a friendly name fit for human consumption. This
document does not propose any specific syntax for the label part.
Note that in some cases it may be helpful to include in the label
some indication of the kind and/or size of the resource referenced by
the URI.
Note that the label may include any characters allowed by the
caseExactString syntax, but that the use of non-IA5 (non-ASCII)
characters is discouraged as not all directory clients may handle
them in the same manner.
Schema Definition of the labeledURIObject Object Class
Name: labeledURIObject
Description: object that contains the URI attribute types
OID: umichObjectClass.15 (1.3.6.1.4.1.250.3.15)
SubclassOf: top
MustContain:
MayContain: labeledURI, labeledURL
Discussion of the labeledURIObject Object Class
The labeledURIObject class is a subclass of top and may contain the
labeledURI and labeledURL attributes. The intent is that this object
class can be added to existing directory objects to allow for
inclusion of URI values. This approach does not preclude including
the labeledURI and labeledURL attribute types directly in other
object classes as appropriate.
References
[1] Berners-Lee, T., Masinter, L., and McCahill, M., "Uniform
Resource Locators (URL)", RFC 1738, CERN, Xerox Corporation,
University of Minnesota, December 1994,
<URL:ftp://ds.internic.net/rfc/rfc1738.txt>
[2] The Directory: Overview of Concepts, Models and Service. CCITT
Recommendation X.500, 1988.
[3] Information Processing Systems -- Open Systems Interconnection --
The Directory: Overview of Concepts, Models and Service. ISO/IEC JTC
1/SC21; International Standard 9594-1, 1988.
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[4] Howes, T., Rossen, K., Sataluri, S., and Wright, R., "Procedures
for Formalizing, Evolving, and Maintaining the Internet X.500
Directory Schema", Internet Draft (Work In Progress) of the Schema
Working Group, <URL:ftp://ds.internic.net/internet-drafts/
draft-howes-x500-schema-03.txt>
Security Considerations
Security considerations are not discussed in this memo.
Acknowledgments
Paul-Andre Pays, Martijn Koster, Tim Howes, Rakesh Patel, and Russ
Wright provided invaluable assistance in the creation of this
document.
This material is based upon work supported by the National Science
Foundation under Grant No. NCR-9416667.
Author's Address
Mark Smith
University of Michigan
Information Technology Division
535 W. William St.
Ann Arbor, MI 48103-4943, USA
Phone: +1 313 764-2277
Fax: +1 313 765-5140
EMail: mcs@umich.edu
This Internet Draft expires April 11, 1995.
Smith IETF ASID Working Group [Page 5]
