W3C home > Mailing lists > Public > w3c-sgml-wg@w3.org > December 1996

Re: unmarked linkend awareness by XML engines

From: David G. Durand <dgd@cs.bu.edu>
Date: Sat, 28 Dec 1996 18:35:09 -0500
Message-Id: <v02130502aeeb4173d49f@[]>
To: w3c-sgml-wg@www10.w3.org
At 12:51 PM 12/28/96, Steven R. Newcomb wrote:
>(Jon Bosak:)
>  "Will XML engines will be responsible for `knowing' that a linkend
>   is a linkend when such a linkend is *not* marked up as a linkend?"
>I still haven't yet seen consensus explicitly emerge on this question,
>although there has been plenty of good and relevant discussion.

I say absolutely not. In some sense the entire web is a candidate, and this
knowledge is impossible. Link targets will in general not know that they
are targets. We will have a bag of kludges and heuristics to deal with this
fact (Altavista, anyone), but we cannot change it.

>(Dave Durand:)
>.... Points of agreement deleted.
>> Which documents are
>> processed is not necessarily our concern.
>I disagree with this assertion.  If XML supports ilinks, there must
>certainly be a way of establishing a finite list of links for which
>the XML engine is responsible for knowing the anchors (er,

No, this is at least in part the user's responsibility. The engine must be
responsible for being able to provide information about links _contained
in_ a document. Other links to that document will only be found if the user
has explicitly or implicitly (via some strategy) specified what other
documents may contain ilinks of interest (for example by opening a bookmark
set of ilinks, or a guided tour set of ilinks, or an annotation set of
links, etc.).

>(Otherwise, the XML engine must be responsible for all
>the XML links on the entire Web, which I think we all agree is an
>insupportable scenario.)  This means establishing, somehow, a finite
>list of documents that contain such links.  HyTime calls such a finite
>list a "Bounded Object Set" (BOS).  In HyTime, the BOS is always
>application-definable, but it is also expressible interchangeably, as
>a suggestion, in terms of an arbitrarily pruned entity tree.  If XML
>supports ilinks, or n-directional linking, or, therefore, what I have
>been imprecisely terming "anchor awareness," I think it's necessary to
>have a way of expressing this pruned entity tree (BOS) notion in XML,

No, we simply have to face the fact that end users are the only ones who
can decide what documents need to be in their processing set. We can't
check the whole world, and we can't just leave it to the author (without
damaging the ability to create external annotations), so we have to leave
it to the user (via their application). In other words, XML as a standard
cannot enforce this kind of scoping for the user. All that we need to
specify is how ilinks behave in documents where they are _parsed_ by an XML
processor. In HyTime terms, the BOS will always be the entire web (one of
the reasons I always thought the notion was limited in usefulness).
However, the set of documents an XML processor will be required to
processes is an application (user) decision. As an example we could not
force a browser to pre-fetch linked documents in case they might reference
ilinks that _might_ be of interest.

    We may well want to consider adding additional notations to express
that some document _may_ be processed when a document is processed. Sort of
a "This document best when parsed along with ..." notation.

   -- David

I am not a number. I am an undefined character.
David Durand              dgd@cs.bu.edu  \  david@dynamicDiagrams.com
Boston University Computer Science        \  Sr. Analyst
http://www.cs.bu.edu/students/grads/dgd/   \  Dynamic Diagrams
--------------------------------------------\  http://dynamicDiagrams.com/
MAPA: mapping for the WWW                    \__________________________
Received on Saturday, 28 December 1996 18:28:40 UTC

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