[whatwg] Proposal: add attributes etags & last-modified to <link> element.

Robert O'Callahan robert at ocallahan.org
Sun Sep 19 13:33:52 PDT 2010

2010/9/19 Julian Reschke <julian.reschke at gmx.de>

> So it's a workaround that causes a performance optimization. It wouldn't be
> necessary if the linked resource would have the right caching information in
> the first place

I think you're misunderstanding the proposal.

 If present for an http uri, these tags represent an assertion about the
> current cache status of the target resource.  A browser that has a cached
> resource for that uri with the same etags and/or last-modified may present
> the link data without validation in connection with the link retrieval.

So for example, page A links to resource B. The browser does a GET on A, and
receives a document containing a <link> to B, and the <link> element has
etags or last-modified attributes. The browser has a cached resource for B,
whose etags/last-modified matches the <link> attribute, so the browser knows
its cached B is valid and no further network transactions are required.

The linked resource B "having the right caching information in the first
place" (when the browser first fetched it) isn't enough to eliminate the
need for an HTTP transaction to validate B later.

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