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Re: Next ZIG - new record type / How to request a spcific schema for XML records?

From: Sebastian Hammer <quinn@indexdata.dk>
Date: Sun, 11 Mar 2001 08:55:56 +0100
Message-Id: <4.2.0.58.20010311084424.016fcab0@bagel.indexdata.dk>
To: Robert Waldstein <wald@library.ho.lucent.com>, www-zig@w3.org
At 10:58 09-03-01 -0500, Robert Waldstein wrote:

> > The other place where I predict we will soon need to identify XML schemas
> > is in the query, where we would like to address specific elements by tag
> > path (preferably by using the existing XPath syntax) rather than by USE
> > attributes. In a community that defines itself by XML-based data models,
> > the tag-paths, after all, are probably the closest thing to abstract 
> access
>
>   (ignorant question warning)
>
>Do you need a schema to use XPATH? I had the impression that you could use
>XPATH style access to XML data independent of knowing anything about the
>DTD/schema/or similar structural concepts.
>   If this is true you could put XPath strings in as attribute strings - might
>want to indicate it is an "XPath string" - in which case might want an OID
>saying "XPath", but would that then be sufficient?

(ignorant response warning)

To be honest, I don't know. If the client only supports one schema (or 
similar concept), or if they all share a certain level of structure, then 
yes, the client shouldn't have to say anything. But this seems to me to go 
against the grain of what Z39.50 is arguably good at - which is to separate 
local physical representation from shared abstractions. To put it 
differently, what if the server internally stores documents in a specific 
schema, but it has crosswalks to any number of other schemas to use for 
searching or retrieval. It seems to me to be desirable to be able to treat 
an XPath expression as an abstract thing - one that can be mapped into 
diffferent sorts of access point spaces.

Again, to me it seems that for this to work well, the client should 
indicate clearly what schema *it* thinks it is addressing, to allow the 
server to make an intelligent judgment.

But you're raising a real issue here... Ideally, I need my query to state 
BOTH that I am providing an XPATH expression and that I think it fits in 
with a certain schema. There's no standard way to identify a schema in the 
XPath expression itself, is there?

--Sebastian
--
Sebastian Hammer        <quinn@indexdata.dk>            Index Data ApS
Ph.: +45 3341 0100    <http://www.indexdata.dk>    Fax: +45 3341 0101
Received on Sunday, 11 March 2001 02:56:06 UTC

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