Processing potentially invalid URI and IRI References

Abstract

The parsing of Uniform Resource Identifiers (URIs, RFC 3986) and Internationalized Resource Identifiers (IRIs, RFC 3987) is defined in terms of Augmented Backus-Naur Form (ABNF). The ABNF grammars are defined in terms of valid identifiers, and thus technically do not address how to handle invalid ones.¶

The URI specification however includes a note how to use Regular Expressions for parsing, and this note applies to invalid identifiers as well. This document introduces terminology referring to potentially invalid identifiers, and demonstrates how the rules in the URI specification can be applied to them.¶

Status of This Memo

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This Internet-Draft will expire in January 2012.¶

Copyright Notice

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.¶

Editorial Note (To be removed by RFC Editor before publication)

Distribution of this document is unlimited. Although this is not a work item of the IRI Working Group, comments should be sent to the IRI mailing list at public-iri@w3.org, which may be joined by sending a message with subject "subscribe" to public-iri-request@w3.org.¶

Discussions of the IRI Working Group are archived at <http://lists.w3.org/Archives/Public/public-iri/>.¶

XML versions, latest edits, and the issues list for this document are available from <http://greenbytes.de/tech/webdav/#draft-reschke-ref-parsing>.¶

Issues list

Id	Type	Status	Date	Raised By
combine-valid	change	open	2011-07-03	derhoermi@gmx.net
edit	edit	open	2011-07-02	julian.reschke@greenbytes.de
iri	change	open	2011-07-02	julian.reschke@greenbytes.de
post	change	proc	2011-07-02	julian.reschke@greenbytes.de
pre	change	proc	2011-07-02	julian.reschke@greenbytes.de
proc	change	proc	2011-07-02	julian.reschke@greenbytes.de

I edit (type: edit, status: open)
julian.reschke@greenbytes.de	2011-07-02	Umbrella issue for editorial fixes/enhancements.

I iri (type: change, status: open)
julian.reschke@greenbytes.de	2011-07-02	Expand for IRIs.

I proc (type: change, status: proc)
julian.reschke@greenbytes.de	2011-07-02	Re-state the parsing algorithm as a procedural algorithm, maybe in JS?
derhoermi@gmx.net	2011-07-03	We can turn the regular expression into a concise ABNF grammar if that helps, we might also adapt it if that is found to be necessary, but I do not see a reason why hundreds of lines of prose code or JavaScript code would help (and anyone who would like to have that anyway can easily de- rive it from the expression or from a grammar).

I pre (type: change, status: proc)
julian.reschke@greenbytes.de	2011-07-02	Define pre-processing steps for extraction of candidate references from content (WS stripping)?

I post (type: change, status: proc)
julian.reschke@greenbytes.de	2011-07-02	Define post-processing steps, such as query component rewriting based on document encoding.

1. Introduction

The parsing of Uniform Resource Identifiers (URIs, [RFC3986]) and Internationalized Resource Identifiers (IRIs, [RFC3987]) is defined in terms of Augmented Backus-Naur Form (ABNF). The ABNF grammars are defined in terms of valid identifiers, and thus technically do not address how to handle invalid ones.¶

2. Terminology

In addition to the terms defined in the URI specification, namely the Syntax Components (see Section 3 of [RFC3986]), this document defines:¶

Candidate URI Reference ¶

A string that may or may not be a valid URI-reference according to Section 4.1 of [RFC3986].

Candidate Scheme Component ¶

A string that may or may not be a valid URI scheme component according to Section 3.1 of [RFC3986].

Candidate Authority Component ¶

A string that may or may not be a valid URI authority component according to Section 3.2 of [RFC3986].

Candidate Path Component ¶

A string that may or may not be a valid URI path component according to Section 3.3 of [RFC3986].

Candidate Query Component ¶

A string that may or may not be a valid URI query component according to Section 3.4 of [RFC3986].

Candidate Fragment Component ¶

A string that may or may not be a valid URI fragment component according to Section 3.5 of [RFC3986].

3. Processing

3.1. Parsing a Candidate URI Reference into Components

The regular expression given in Appendix B of [RFC3986] will parse any input string into a Candidate Scheme Component, a Candidate Authority Component, a Candidate Path Component, a Candidate Query Component, and a Candidate Fragment Component. Note that of these five components, all components except for the Path Component can be undefined.¶

If each of the defined components is valid according to the related URI component definition, the input was a valid URI reference.¶

3.2. Resolution of Candidate References

I combine-valid (type: change, status: open)
derhoermi@gmx.net	2011-07-03	In section 3.2 you have "The result will be a valid URI Reference if and only if the components used by the algorithm were valid themselves." I have some doubts about "only if", consider for instance removing dot segments, which might remove a malformed part, if I recall correctly.

Section 5 of [RFC3986] defines Reference Resolution based on the five components. This algorithm works both for components obtained from valid and invalid references. The result will be a valid URI Reference if and only if the components used by the algorithm were valid themselves.¶

4. Security Considerations

[rfc.comment.1: TBD] ¶

5. IANA Considerations

There are no IANA Considerations related to this specification.¶

6. References

6.1. Normative References

[RFC3986]: Berners-Lee, T., Fielding, R., and L. Masinter, “Uniform Resource Identifier (URI): Generic Syntax”, STD 66, RFC 3986, January 2005.

6.2. Informative References

[RFC3987]: Duerst, M. and M. Suignard, “Internationalized Resource Identifiers (IRIs)”, RFC 3987, January 2005.