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Locating LinkBase

From: Licia Capra <l.capra@cs.ucl.ac.uk>
Date: Wed, 12 Jul 2000 15:34:24 +0100
Message-ID: <396C81F0.C11459C6@cs.ucl.ac.uk>
To: "Eve L. Maler" <Eve.Maler@east.sun.com>, www-xml-linking-comments@w3.org
Hello Eve,

let's see if I understood the point ...

I have a set of (in my case XML) documents that represent the starting
resources (or better, some elements inside them are my starting
resources); then I have my tool that generates linkbases that I use to
keep track of links between elements in different documents.
What I need now is a way to associate a starting resource with its
linkbases (possibly more than one). This information must be kept in a
third file (let's call it "basesLoaded" ... a name I've found in the
XLink specification :) that my application reads each time I ask to
apply a linkbase to a starting resource.
So these are the steps:

1) load the basesLoaded --> as a result, I obtain a list of linkbases I
can apply to my starting resource
2) apply the selected linkbase to the staring resource

Could it work?



> Hello,
> my name is Licia Capra and I am a PhD student at University College
> London.
> At the moment I am involved in a project that requires the usage of
> XLink, in particular to manage a set of "third_party" links. The problem
> I have to face is how to locate both the starting resource and the
> links.
> I have read the XLink specification where you talk about Linkbases and
> arcrole attribute, but I couldn't understand how things work. My set of
> third_party links is contained in an xml file containing all (and only)
> the links I am interested into ... that is in fact a linkbase, isn't it?

Yes, any XML document containing extended links is a linkbase.  Even if 
your file contained all kinds of other stuff, it could still be a
but it's nice and clean if it only contains links (you might want to add 
some "metadata" markup describing the characteristics of the

>But now, how can I locate this file (the linkbase) and instruct the
>browser to use this file to fetch the links that are of interset for my
>source document?

There are many ways.  The specification offers one way, but:

- It is incomplete.

   You sort of have to bootstrap your system to find a linkbase arc
   somehow.  If you have a linkbase arc that traverses from the
   document to the linkbase, you're okay.  But if the starting resource
   is in some other document, you still have the (even more indirect)
   problem of how to locate the linkbase arc.

- You are free to use any method you like to locate linkbases in order
   to load them.

   You're not constrained to use linkbase arcs; you can simply declare
   that, in your system, you will (e.g.) look for a "linkbase
   file" in a particular location in order to find a list of linkbases.

In fact, I think a good solution would be a combination: Declare that
XLink application will, by default, look in a certain location for an
document that contains linkbase arcs.  This is of course partially 
implementation-dependent, but I think it will be valuable to leave this 
unconstrained for now and see what the market/user community comes up

>Another question: do you know if there exists a browser that supports
>xlink specification?

I've been told that Mozilla attempts to support simple links, but I
have personal experience and don't know how good a job it does.  I don't 
know of any browser that supports extended links yet.

> "Eve L. Maler" wrote:
> At 09:46 AM 7/12/00 +0100, Anthony Finkelstein wrote:
> >Hmmm. I am very grateful for Eves excellent reply but ... I am not sure
> >that the solution proposed by Eve is, in fact, the appropriate way to
> >handle things. In our case we generate a "3rd party linkbase" and hand the
> >owner of the source document the URL of that linkbase.
> >
> >We may generate several different linkbases each to be seperately
> >"applied" to the document set. In this case the default linkbase location
> >does not really work because how do they select which linkbase to apply?
> >
> >We need something which works like an xsl processor in which we explicitly say
> >
> >apply [linkbase] to [document]
> >
> >BUT OUTSIDE THE DOCUMENT! Its important not to modify the source document.
> I agree with you here.  An in-band solution is just a stopgap; out-of-band
> is needed in the general case.  The linkbase arc can be used in both ways,
> such that if its starting resource is not in the current document (it's not
> quite accurate to say "remote," actually), it functions just like your
> made-up "apply" command above, and would be executed by an XLink application.
> >I am a bit depressed at the thought that this is all subject to the
> >vagaries of how the browser handles it as this leaves automated linkbase
> >generators up the spout.
> Not really; it just doesn't leave them with a completely interoperable way
> of doing so.  I would encourage you to send mail to
> www-xml-linking-comments@w3.org on this subject, to ensure that we discuss
> it...  Feel free to quote any of my responses as you wish.
>          Eve
> --
> Eve Maler                                    +1 781 442 3190
> Sun Microsystems XML Technology Center    elm @ east.sun.com
Received on Wednesday, 12 July 2000 10:39:58 UTC

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