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Re: request for practical usage examples of XQuery

From: Donald Spaeth <donald@spaeth.freeserve.co.uk>
Date: Mon, 9 Jun 2003 10:10:09 +0100
Message-ID: <007701c32e66$edbe00e0$12984c51@D9BKQB0J>
To: "'Joris Graaumans'" <joris@cs.uu.nl>, <www-ql@w3.org>

Michael Kay wrote:
> It would be very interesting to find out if that is true. I see XSLT being
> used quite a lot for tasks I would describe as query, and XQuery being
> for tasks I would describe as transformation...

I couldn't agree more.  I've spent the last year developing stylesheets for
querying historical data using XSLT.  I haven't had a chance to investigate
XQuery properly yet, so I'm not yet sure it will do what I want.  Historical
source materials are good examples of semistructured data, but they have
been conventionally represented as relational tables.  The challenge is to
represent the structure as it appears, but to query the data as if they
consisted of relational tables.  (Representing the data as literal
relational tables with ID numbers, as in the XML Query Use Cases example, is
a less interesting way of addressing the problem.)

Typical applications involve constructing frequencies and contingencies
tables which count particular element values, usually based upon
standardised data; and preparation of coded data in  matrices for analysis
in statistical software.  For example, one might count the number of rooms
per house, and see how these changed over time, or count the number of halls
with cooking equipment.  (My research is based upon lists of household goods
from the seventeenth century.)  All of this can be done in XSLT.

If we set aside XSLT syntax errors (very common!), the most frequent errors
result from confusion about what the current unit of analysis is and where
one is in the hierarchy.  I find myself checking and double-checking that
nodesets have the information I expect them to have.

Donald Spaeth

Dr Donald Spaeth
Senior Lecturer in Historical Computing
Department of History
2 University Gardens
University of Glasgow
Glasgow  G12 8QQ

tel. 0141 330 3580
reply to:  d.spaeth@history.arts.gla.ac.uk
Received on Monday, 9 June 2003 05:09:54 UTC

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