RFC 2079

RFC 2079: Defining an X.500 Attribute Type and Object Class for URIs 🎀

okay bestie, this one is from January 1997 and it's from the Network Working Group 🌸 It was written by Mark Smith (M. Smith) at Netscape Communications, and it's on the Standards Track 💅 It doesn't list anything it obsoletes or updates, so it's a pretty clean start ✨

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Status of This Memo 📜

this doc is an Internet standards track protocol for the Internet community, and it's asking for discussion and suggestions for improvements 💖 For the standardization state and status of this protocol, check the current edition of the "Internet Official Protocol Standards" (STD 1) 🧚 Distribution of this memo is unlimited 🌈

Abstract ✨

URLs are everywhere now, used to point at Internet resources 🦋 There's a real need to put them into directories that follow the LDAP and X.500 information models, and people also want other kinds of URIs in there as those get defined 💜 A bunch of independent groups were already trying to stick URLs into LDAP and X.500 directories, and this doc builds on that experimenting 🔥 It defines a new attribute type and an auxiliary object class so URIs (URLs included) can be stored in directory entries in a standard way 👑

Background and Intended Usage 🌸

URLs, as defined in [1], are the first of several kinds of URIs the IETF is defining 🫶 URIs are super popular on the Internet, especially inside HTML documents [2] 💅 This doc defines an X.500 [3,4] attribute type called labeledURI and an auxiliary object class called labeledURIObject to hold all kinds of URIs, URLs included ✨ They're made for LDAP and X.500 directories, but they can be used in other contexts too 🎀

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 💬

okay so the labeledURI attribute uses the caseExactString syntax, because URIs are case-sensitive, and it's multivalued 💖 Each value should be a URI (right now, that means a URL), optionally followed by one or more space characters and then a label 🦋 Spaces aren't allowed un-encoded inside URIs, so there's zero ambiguity about where the label starts 🙈 For now, the URI part has to follow the URL specification in [1] 🔥

Multiple labeledURI values usually mean different resources that all relate to the X.500 object 🧚 They can also be different locations for the same resource ✨

The label describes the resource the URI points to, and it's meant to be a friendly name that humans can read 🌈 This doc doesn't propose any specific syntax for the label 💅 Sometimes it helps to put the kind and/or size of the resource in the label 📦

Heads up: the label can use any characters that caseExactString allows, but non-IA5 (non-ASCII) characters are discouraged 😭 Not every directory client handles them the same way 💀 If you do include non-IA5 characters, use X.500 conventions, not HTML ones 🫶 For example, an "a" with a ring above it should be encoded with the T.61 sequence 0xCA followed by an "a" character, and you should not use the HTML escape &aring 🚫

Examples of labeledURI Attribute Values 🍓

here are some examples, bestie 🧚

An example with no label:

ftp://ds.internic.net/rfc/rfc822.txt

An example with a tilde in the URL. Special characters in a URL have to be encoded the way the URL document [1] says. The label is "LDAP Home Page":

http://www.umich.edu/%7Ersug/ldap/ LDAP Home Page

Another one! This label has a hint so the user knows the URL points to a photo image 📸

http://champagne.inria.fr/Unites/rennes.gif Rennes [photo]

Schema Definition of the labeledURIObject Object Class 🧩

Name:              labeledURIObject
Description:       object that contains the URI attribute type
OID:               umichObjectClass.15 (1.3.6.1.4.1.250.3.15)
SubclassOf:        top
MustContain:
MayContain:        labeledURI

Discussion of the labeledURIObject Object Class 🌟

the labeledURIObject class is a subclass of top and may contain the labeledURI attribute 💜 The idea is that you can add this object class to existing directory objects so they can hold URI values 🎀 It doesn't rule out putting the labeledURI attribute type straight into other object classes where that fits 🦋

Security Considerations 🚨

this part is serious, bestie 😭

security isn't really discussed in this memo, except for one big warning: blindly putting the label part of a labeledURI attribute value into an HTML document is not recommended 💀 A malicious person could sneak HTML tags into the label, and those tags could mislead viewers of the whole document where the value got inserted 🙈

Acknowledgments 🫶

Paul-Andre Pays, Martijn Koster, Tim Howes, Rakesh Patel, Russ Wright, and Hallvard Furuseth gave invaluable help in making this doc 👑

This material is based in part on work supported by the National Science Foundation under Grant No. NCR-9416667 ✨

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Appendix: The labeledURL Attribute Type (Deprecated) 🥀

an earlier draft of this doc defined a second attribute type called labeledURL 🕰️ It's deprecated now, so don't use it when adding new values to directory entries 🚫 The original reason for a separate URL attribute was that it would make it easier to programmatically access specific types of URIs 🧠 After some deliberation, the IETF-ASID working group decided one attribute was better than two 💅

The labeledURL schema is kept here for historical reference only 📚 Directory client software may want to support it alongside labeledURI, which helps sites that are still using labeledURL move over to the new one 🦋

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
OID:              umichAttributeType.41 (1.3.6.1.4.1.250.1.41)

References 📚

[1] Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform Resource Locators (URL)", RFC 1738, CERN, Xerox Corporation, University of Minnesota, December 1994. <URL:ftp://ds.internic.net/rfc/rfc1738.txt>

[2] Berners-Lee, T., and D. Connolly, "Hypertext Markup Language - 2.0", RFC 1866. <URL:ftp://ds.internic.net/rfc/rfc1866.txt>

[3] The Directory: Overview of Concepts, Models and Service. CCITT Recommendation X.500, 1988.

[4] Information Processing Systems -- Open Systems Interconnection -- The Directory: Overview of Concepts, Models and Service. ISO/IEC JTC 1/SC21; International Standard 9594-1, 1988.

Author's Address 💌

Mark Smith Netscape Communications Corp. 501 E. Middlefield Rd. Mountain View, CA 94043, USA

Phone: +1 415 937-3477 Email: mcs@netscape.com