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Re: Another pseudo-element gotcha

From: James Clark <jjc@jclark.com>
Date: Tue, 29 Apr 1997 09:38:27 +0700
Message-Id: <>
To: w3c-sgml-wg@w3.org
At 16:47 28/04/97 GMT, Peter Murray-Rust wrote:

>If you think of a scientific publication, you can think of it having 
>components (graphs, tables, molecules, figures, citations, etc) and all
>of these will vary from publisher to publisher in order and amount.
>It's quite meaningful and possible to ask:
>	'please extract all molecules from this paper'
>	'extract all molecules which contain spectra'
>(notice the word 'all').  In general we shall not know how many molecules
>there are in the paper or what order they come in.

I can easily imagine this as part of processing.  What I am still having a
hard time seeing is why this sort of thing needs to go in an extended link
or a simple link in an XML document.

If you want to do this sort of thing, what you need is a fully-fledged query
language.  If you try to use xpointers for this, you will continually be
finding things you want to express, but can't.

>This assumes that you know that you need to count 17 along.  When you
>have no idea of the structure of the document, other than the components
>it may contain (but not the level they may occur at or their order), the
>tools that are currently suggested are ideal.

I think this is the heart of the issue.  There seem to me to be two kinds of

a) I have a collection of specific documents, and I want to create links
between those specific documents.

b) I have an open-ended class of documents, and I want to describe
processing that works on any document in the class.

For (a), I think a cut-down version of xpointers does what's needed.  For
(b), which seems to be what you're doing, a cut-down version of xpointers
won't be adequate, but neither, I would suggest, would an enhanced version
be adequate: (b) is what DSSSL is mainly about, and for that you need a full
query language.

Received on Monday, 28 April 1997 22:52:50 UTC

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