From: Stuart Langridge (firstname.lastname@example.org)
Date: Fri Sep 06 2002 - 19:17:28 BST
Jim Dabell spoo'd forth:
> Hi, hope this is a public mailing list, and it's okay to post and not just
> lurk - I came across this list by accident, so I'm not sure :)
No worries, get stuck in ;)
[pingback <link> tag]
> There are a couple of negatives, of course, that have been brought up:
> - - need control over http headers
> This will only affect static blogs, surely? I just checked in php, and that
> can certainly affect headers via a http head, and I'd imagine everything
> else can as well.
A lot of blogs *are* static, though, because they build static pages
for rendering speed, even if you do have CGI access to the headers. If
I were using static pages I certainly wouldn't want to do the overhead
of kaing all my pages a CGI.
> - - head is not well supported
> This is the first I've heard about this. What servers don't support head?
I must confess that I'm taking someone else's word for this. However,
the someone is Jamie Zawinski, who I expect to know about this stuff.
>From http://www.jwz.org/hacks/marginal.html: "...then does a GET on
each of them (not a HEAD, because that doesn't work with all sites)..."
> - - pingback checks to make sure the permalink url is actually in the page
> It seems to me that this should be an optional part of the spec anyway -
> some implementations won't want the overhead.
I don't agree here. Checking for a reference prevents pingbacks being
spammed or flooded. I've seen too many examples of protocols where
people think of this sort of thing later on and find that it's a real
pain to retrofit; if we make it part of the spec up front then we'll
never have to worry about it.
> Which (in a roundabout way) leads me to my next question:
> What are the semantics for changing pages? Suppose you get a pingback, and
> the referring page deletes the reference to you? Or the site goes offline,
> never to come back?
Ah, but Cool URIs Don't Change, remember?
I'm not necessarily seeing a need to cope with this; after all, links
that have been blogged may go dead or move and no-one worries about
that particularly, I don't think?
Technically the referring site may delete the reference to you, it's
true, but I don't think that that happens very often...
I also don't agree with the link being in the headers for two further
reasons, which are possibly facets of one big reason: it ain't right.
1. You should be able to tell a page's pingback URL from the page in
isolation, because it relates to the page. HTTP headers aren't the page
at all, they're merely the method by which the page is served, which
should be irrelevant to what you do with its content. It would be
possible to serve a site from an ftp server (if you were a nutter) and
you might still request pingbacks, but there would be no headers -- how
a page is given to the user is irrelevant. It's the content that's
2. Headers are invisible and weird techie things. It'll be jolly
difficult to explain them to people (although, I admit, my plan for
pingback is that it happens automatically without user intervention).
3. The LINK tag is, in my opinion, the Right Way to show stuff related
to a page, like alternative representations or CSS that relates to it.
That's what it's designed for, and that's how it should be used, I
think; it's clearly the way to show the pingback server related to a
I'd be interested in further comments here...
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