RE: Indirection in XQuery/XPath

At one stage XQuery had a fairly general-purpose mechanism for following
references from one node to another. However, it was never defined very
precisely. The difficulty is that there are too many different ways of
defining relationships in XML: IDREF, URIs, XPointer, application-defined
foreign keys, schema-defined key/keyref, and so on.
 
In fact there is a very general mechanism in XQuery that can handle all of
these - the function call. I think this is the right mechanism, though if
support for a particular technique such as XPointer becomes widespread, then
we should probably provide a specific function to handle it within the core
function library.
 
Michael Kay

-----Original Message-----
From: Shlomo Geva [mailto:s.geva@qut.edu.au] 
Sent: 03 March 2003 22:19
To: public-qt-comments@w3.org
Cc: sihem@research.att.com; marx@science.uva.nl
Subject: Indirection in XQuery/XPath


Hi There,

The ability to follow links and pointers (or anchors) is probably worthwhile
considering.  Take a query such as - "get all paragraphs that contain a
citation of a paper authored by Kohonen".   This is a common requirement in
bibliography searching where you want the exact context of the citation.
If the citation reference is implemented as an anchor (XPointer?) then it
will not include explicit author details and hence the paragraphs cannot be
selected directly by using "Kohonen" as a search argument.  Rather, having
found Kohonen in the bibliography section of an article we need to take the
citation-id and use it as a search argument in paragraphs selection
(indirection).
This may be too complex a requirement, but it is certainly a "nice to have".
(This is akin to performing a join following a foreign key in an SQL query)

It can be further enhanced if we were to support following links (XLink?) to
other documents - for instance, extend the example above to include
selection terms that can only be got at by inspecting the cited Kohonen
paper itself (i.e, another document altogether).  Indirection following
XLinks and XPointers would be a really nice feature in a retrieval engine,
albeit perhaps too complicated as an explicit and bare user interface
feature.  

Regards,

Shlomo




Shlomo Geva, PhD
Centre for Information Technology Innovation
(Office: 126 Margaret St, Room 306)
Faculty of Information Technology
Queensland University of Technology
GPO Box 2434, 
Brisbane, Q 4001, AUSTRALIA

* Phone: +61 7 3864 9326
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* Email: s.geva@qut.edu.au