Internet DRAFT - draft-borden-frag
draft-borden-frag
Network Working Group J. Borden
Internet-Draft The Open Healthcare Group
Expires: August 20, 2002 S. St.Laurent
February 19, 2002
A generic fragment identifier syntax for URI references
draft-borden-frag-00.txt
Status of this Memo
This document is an Internet-Draft and is in full conformance with
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Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
URI references with fragment identifiers uniquely identify parts of a
document. Such identifiers have been specified as SGML/XML IDs e.g.
in HTML [6]. The XPointer [2] specification is intended to serve as
a fragment identifier syntax for XML documents. IDs conform to the
XPointer "raw name" form. Specifications constraining the behavior
of user agents such as SMIL [8], XHTML [15], and SVG [10] have all
supported this simple fragment naming convention though some extend
it.
Specifications such as XML Namespaces [4] and RDF [16] use URI
references as opaque names. Such usage does not depend on resolution
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of the URI. In such usages, no media type is specified and the
proper fragment identifier syntax is undefined. As it has become
common practice to use URI references as opaque identifiers, this
proposal seeks to provide a minimal definition of what might be
identified by a URI reference.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Subresource . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Numeric fragments . . . . . . . . . . . . . . . . . . . . . . 6
5. Scheme based fragments . . . . . . . . . . . . . . . . . . . . 7
6. Declaration of support for schemes . . . . . . . . . . . . . . 8
7. General Syntax . . . . . . . . . . . . . . . . . . . . . . . . 9
References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 11
A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
B. Revision History . . . . . . . . . . . . . . . . . . . . . . . 13
Full Copyright Statement . . . . . . . . . . . . . . . . . . . 14
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1. Introduction
Frequently URI references [1], which may contain a fragment
identifier, are used independent of their resolution into a
particular document, or document fragment, at a particular point in
time.
A notable example is use of a URI reference as an XML Namespace [4]
name. In the current situation a the syntax of the fragment
identifier part of a URI reference is defined by the MIME media type
of the referenced document as in an HTTP transaction. This media
type is not fixed, and may change from time to time and from
reference to reference, or according to request headers such as with
content negotiation.
Fragment identifier syntax, in practice, is often constant from media
type to media type. In order to enable robust use of fragment
identifiers, particularly outside a particular HTTP transaction, we
propose a generic, media type independent, fragment identifier
syntax. This fragment identifier syntax is compatible with current
usage of fragment identifiers, and is generally compatible with
future proposed syntaxes such as XPointer [2].
This specification does not itself specify how user agents are to
process or interpret fragment identifiers, such as may be specified
with individual MIME media type registrations, rather provides a
consistent syntax for fragment identifiers and a registration
mechanism for schemes associated with fragment identifier syntaxes.
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2. Subresource
A subresource is identified by a URI reference in the same fashion
that a resource is identified by a URI. The relationship between a
subresource and fragment of a document entity is the same as the
relationship between a resource and the entity returned by resolving
the URI.
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3. Names
The short form of a fragment identifier is a Name. A Name is used as
the fragment identifier for HTML, and is equivalent to the Bare Name
form of XPointer [2]. This proposal does not define any mechanism of
locating document fragments by name, leaving this up to the
application
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4. Numeric fragments
A numeric fragment is of the form: ('/' Number)+ e.g. #/10/24 This
conforms to the XPointer [2] Child Sequence syntax, however may be
used by non-XML media types. For example a particular frame of a
video clip might be represented as: #/100025 ranges are expressed as
/1-10 and lists as /1,2,5,20
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5. Scheme based fragments
The full form of a fragment identifier uses the Scheme '(' string ')'
Form. This form is consistent with the XPointer [2] full xpointer
form, hence this valid full XPointers conform to this proposed
syntax. This specification defines the following scheme names:
xpath: the content is a valid XPath [5]
-- xpath(//foo[1])
xmlns: the content defines a namespace prefix mapping
-- xmlns(ex=http//example.org/xmlns/)
xpointer: the content is a valid XPointer
-- xpointer(/foo/bar[1])
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6. Declaration of support for schemes
A namespace may declare support for a particular scheme or set of
schemes via a RDDL [7] description. The id of a RDDL resource
describing a scheme should be the same as the name of the scheme.
The RDDL nature or the resource should be URI reference identifying
the scheme. The RDDL purpose of the scheme should be the URI: http:/
/www.rddl.org/fragment-syntax#scheme. For example:
<div id="xpointer">
<rddl:resource
xlink:arcrole="http://www.rddl.org/fragment-syntax#scheme"
xlink:href="http://www.w3.org/TR/xptr"
/>
</div>
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7. General Syntax
FragmentId ::= Name | NumberPart | (FragmentPart (S? FragmentPart))
NumberPart ::= ('/' , Number,(('-'|','),Number))*)+
FragmentPart ::= Scheme '(' SchemeSpecificExpr? ')'
SchemeSpecificExpr ::= StringWithBalancedParens
StringWithBalancedParens ::= [^()^^|^^^^|^^)|^^(]* ('(' StringWithBalancedParens
')' [^()^^|^^^^|^^)|^^(]*)*
'^^' escapes '^', '^)' escapes ')' and '^(' escapes '('
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References
[1] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax", RFC 2396, August
1998.
[2] DeRose, S., Daniel Jr., R. and E. Maler, "XML Pointer Language
(XPointer)", World Wide Web Consortium Candidate Recommendation
xptr, September 2001, <http://www.w3.org/TR/xptr>.
[3] Bray, T., Paoli, J. and C. Sperberg-McQueen, "Extensible Markup
Language (XML) 1.0", World Wide Web Consortium Recommendation
REC-xml, February 1998, <http://www.w3.org/TR/REC-xml>.
[4] Bray, T., Hollander, D. and A. Layman, "Namespaces in XML",
World Wide Web Consortium Recommendation REC-xml-names, January
1999, <http://www.w3.org/TR/REC-xml-names/>.
[5] Clark, J. and S. DeRose, "XML Path Language (XPath) Version
1.0", World Wide Web Consortium Recommendation xpath, November
1999, <http://www.w3.org/TR/xpath>.
[6] Raggett, D., Le Hors, A. and I. Jacobs, "HTML 4.01
Specification", World Wide Web Consortium Recommendation html4,
December 1999, <http://www.w3.org/TR/html4/>.
[7] Borden, J. and T. Bray, "Resource Directory Description
Language (RDDL)", June 2001, <http://www.rddl.org>.
[8] Ayars, J., Bulterman, D., Cohen, A., Day, K., Hodge, E.,
Hoschka, P., Hyche, E., Jourdan, M., Kim, M., Kubota, K.,
Lanphier, R., Layaida, N., Michel, T., Newman, D., van
Ossenbruggen, J., Rutledge, L., Saccocio, B., Schmitz, P. and
W. ten Kate, "Synchronized Multimedia Integration Language
(SMIL 2.0) Specification", World Wide Web Consortium Proposed
Recommendation PR-smil20, June 2001, <http://www.w3.org/TR/
smil20/>.
[9] 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.
[10] Ferraiolo, J., "Scalable Vector Graphics (SVG)", World Wide Web
Consortium Working Draft SVG, August 1999, <http://www.w3.org/
TR/SVG>.
[11] Marsh, J., "XML Base (XBase)", World Wide Web Consortium
Working Draft xmlbase, February 2000, <http://www.w3.org/TR/
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xmlbase>.
[12] DeRose, S., Maler, E., Orchard, D. and B. Trafford, "XML
Linking Language (XLink)", World Wide Web Consortium Working
Draft xlink, July 1999, <http://www.w3.org/TR/xlink/>.
[13] Clark , J., "XSL Transformations (XSLT) Version 1.0", World
Wide Web Consortium Recommendation xslt, November 1999, <http:/
/www.w3.org/TR/xslt>.
[14] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629, June
1999.
[15] Pemberton, S. and et al, "XHTML 1.0: The Extensible HyperText
Markup Language", World Wide Web Consortium Recommendation REC-
xhtml1, January 2000, <http://www.w3.org/TR/xhtml1>.
[16] Lassila, O. and R. Swick, "Resource Description Framework (RDF)
Model and Syntax Specification", World Wide Web Consortium
Recommendation REC-rdf, February 1999, <http://www.w3.org/TR/
REC-rdf-syntax/>.
Authors' Addresses
Jonathan Borden
The Open Healthcare Group
114 Merriam Street
Weston, MA 02493
US
EMail: jonathan@openhealth.org
URI: http://openhealth.org/
Simon St.Laurent
1259 Dryden Road
Ithaca, New York 14850
USA
EMail: simonstl@simonstl.com
URI: http://www.simonstl.com/
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Appendix A. Acknowledgements
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Appendix B. Revision History
[To be deleted before publication.]
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Full Copyright Statement
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