Re: [apps-discuss] [link-relations] Fwd: I-D Action: draft-ohye-canonical-link-relation-00.txt
Joachim Kupke <joachim@kupke.za.net> Thu, 21 July 2011 03:48 UTC
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From: Joachim Kupke <joachim@kupke.za.net>
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Cc: "link-relations@ietf.org" <link-relations@ietf.org>, IETF Apps Discuss <apps-discuss@ietf.org>, Bjartur Thorlacius <svartman95@gmail.com>
Subject: Re: [apps-discuss] [link-relations] Fwd: I-D Action: draft-ohye-canonical-link-relation-00.txt
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Julian Reschke <julian.reschke@gmx.de> wrote: > Joachim Kupke <joachim@kupke.za.net> wrote: >> Reading paragraph 5 of RFC 2119, I don't see >> anything wrong with >> ‘MAY.’ How is ‘can’ better? It's indeed not a ‘SHOULD’ since a typical >> implementation, say in a search engine, will want to go to some length to >> find evidence for misguided usage of the relationship and in the presence of >> such evidence decide to ignore it. The point of ‘MAY’ is to make clear that >> in the absence of such evidence, the responsibility not to advertise an >> erroneous ‘canonical’ relationship lies with the author of the context URI.” > > See RFC 2119, Section 6: [...] It's true that the imperatives of RFC 2119 (including "MAY"/"OPTIONAL") are supposed to pertain to the format of data that is exchanged (e.g., this and that field MAY be omitted, or this and that proxy MAY have rewritten something), but interoperability goes beyond that; hence the desire to give the two points where MAY is used in the draft some more formal meaning. Specifically, a <link rel="canonical"> supposedly gives carte blanche to, say, an application to organize bookmarks, to rewrite a bookmarked URI to its rel=canonical variant, if any (and non-self-referential). Or, say, Wikipedia could crawl its external links and automatically update those that now have a "canonical" relationship with another URI (or, for that matter, have become an HTTP 301 redirect). In order not to break such applications, it is fairly important for implementations of rel="canonical" not to designate URIs that are meaningless substitutions for links to the context URI. Speaking of HTTP redirects, RFC 2616 uses the wording that "[c]lients with link editing capabilities *ought to* automatically re-link references" to URIs that have become 301 redirects; and for a 300 "multiple choices" URI, "user agents *MAY* use the Location field value for automatic redirection" (both emphases added). It appears the latter point is no more required for interoperability than what the occurrences of "MAY" in this draft allude to. With that said, it's closer in spirit to the provisions of 301 redirects, so I'd be happy to see the draft changed as follows: diff before after index 5f01f55..4ed47b8 100644 --- before +++ after @@ -66,10 +66,9 @@ Internet-Draft The Canonical Link Relation 1. Introduction The canonical link relation specifies the preferred URI from a set of - identical or vastly similar content accessible on multiple URIs. - This designation MAY be used for future references to this resource, - and clients with link editing capabilities MAY automatically re-link - references to the context URI to the designated URI. + identical or vastly similar content accessible on multiple URIs, to + make it possible for references to the context URI to be updated to + reference the designated URI. The most common application of the canonical link relation includes specifying the preferred version of a URI from duplicate content @@ -86,8 +85,8 @@ Internet-Draft The Canonical Link Relation The canonical (target) URI MUST identify content that duplicates, is extremely similar, or is a superset of the content at the context - (referring) URI. Presence of the canonical link relation indicates - to applications, such as search engines, that they MAY: + (referring) URI. Authors who declare the canonical link relation + ought to anticipate that applications such as search engines can: o Index content only from the canonical target (i.e. content from the context URIs will be likely disregarded as duplicative). --Joachim
- [apps-discuss] Fwd: I-D Action: draft-ohye-canoni… Julian Reschke
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Frank Ellermann
- Re: [apps-discuss] Fwd: I-D Action: draft-ohye-ca… Mykyta Yevstifeyev
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Julian Reschke
- Re: [apps-discuss] Fwd: I-D Action: draft-ohye-ca… Julian Reschke
- Re: [apps-discuss] Fwd: I-D Action: draft-ohye-ca… Mykyta Yevstifeyev
- Re: [apps-discuss] Fwd: I-D Action: draft-ohye-ca… Julian Reschke
- Re: [apps-discuss] Fwd: I-D Action: draft-ohye-ca… Mykyta Yevstifeyev
- Re: [apps-discuss] Fwd: I-D Action: draft-ohye-ca… Mykyta Yevstifeyev
- Re: [apps-discuss] Fwd: I-D Action: draft-ohye-ca… Mykyta Yevstifeyev
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Mykyta Yevstifeyev
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Frank Ellermann
- Re: [apps-discuss] Fwd: I-D Action: draft-ohye-ca… Bjartur Thorlacius
- Re: [apps-discuss] Fwd: I-D Action: draft-ohye-ca… Bjartur Thorlacius
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Justin Cormack
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Mykyta Yevstifeyev
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Julian Reschke
- Re: [apps-discuss] Fwd: I-D Action: draft-ohye-ca… Julian Reschke
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Frank Ellermann
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Julian Reschke
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Joachim Kupke
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Julian Reschke
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Mykyta Yevstifeyev
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Maile Ohye
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Joachim Kupke
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Peter Saint-Andre
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Julian Reschke
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Peter Saint-Andre
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Julian Reschke
- Re: [apps-discuss] [link-relations] Fwd: I-D Acti… Peter Saint-Andre