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Re: Last Call: draft-nottingham-http-link-header (Web Linking) to Proposed Standard

From: Noah Slater <nslater@tumbolia.org>
Date: Mon, 31 Aug 2009 07:50:40 +0100
To: Eran Hammer-Lahav <eran@hueniverse.com>
Cc: Ian Hickson <ian@hixie.ch>, HTTP Working Group <ietf-http-wg@w3.org>
Message-ID: <20090831065040.GA16892@tumbolia.org>
On Sun, Aug 30, 2009 at 11:30:18PM -0700, Eran Hammer-Lahav wrote:
> As for 'up', its definition is too ambiguous to support these combinations. It
> is currently registered as: "A URI that refers to a parent document in a
> hierarchy of documents."

This is arguably a good thing.

> I can't figure out if 'a parent' can be any parent of a direct parent. If it
> means a direct parent, your theory of 'automatically works' breaks because UAs
> will expect the document to be the direct parent, not just a document
> somewhere 'up' there. If it means any parent, then you can't express a direct
> parent, but can express a second direct parent.

For what it's worth, my thoughts were that this would represent a resource that
was a direct parent of the resource. And by direct parent, I mean a parent that
must necessarily be passed through if traversing the hierarchy. For the purpose
of this discussion, however, I'm not sure my original intentions matter.

> If you don't want to register multiple 'up-n' relations, consider defining the
> relation type with an optional extension, such as:
> Link: <http://example.com>; rel="up"; level="2"

I'm going to go out on a limb and suggest that most hierarchical relationships
that people will want to express will be such that the level can be inferred
directly from the URI. More over, I fail to understand what kind of UA interface
would need or want this kind of detail.

> And it would be better if the 'up' registration entry was more clear
> indicating it can indicate *any* parent, not just a direct parent. This way, a
> client always understand what the relation means, but can also support finer
> details with an extension.

I worded it to match the existing relations, which I think are suitably vague.

We're talking about reasonably loose document relations, where UAs should be
free to present this information in similarly loose ways. For most cases I can
imagine, simply listing the "up" relations in the order that they appear in the
document source should be enough. But this is up to them.


Noah Slater, http://tumbolia.org/nslater
Received on Monday, 31 August 2009 06:51:22 UTC

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