RE: XQuery updates and unnormalized data (RE: [xml-dev] A standard approach to glueing together reusableXML fragments in prose?)

["Dare Obasanjo" <dareo@microsoft.com>]

The effects of data redundancy can be reduced if the DML has features such as cascading updates and deletes which is something that many users of XML as a data storage format will require since many are averse to "normalizing" XML. 
 
However, like I said this is a small problem compared to how to reconcile an XQuery DML with a type system based on W3C XML Schema. 

________________________________

From: Jonathan Robie [mailto:jonathan.robie@datadirect.com]
Sent: Mon 8/25/2003 9:34 AM
To: Dare Obasanjo; Mike Champion; xml-dev@lists.xml.org
Subject: XQuery updates and unnormalized data (RE: [xml-dev] A standard approach to glueing together reusableXML fragments in prose?)



At 11:19 AM 8/25/2003, Dare Obasanjo wrote:
>Ah, yes. The main problems with the hierarchical model are that it
>encourages data redundancy which leads to problems during updates and
>deletions. XQuery has dodged the bullet with solving this problem for now
>since the DML work is slated for v-next. Of course, XQuery has bigger
>problems to solve than that whenever DML gets around to being specced
>given its dependency on W3C XML Schema as a type system.

You can have data redundancy with either XML or relational databases. If
you do, there are problems with updates. Persistent stores of XML will need
to normalize data to make consistent updates easy, or else people will have
to maintain a lot more error-prone code for updates. Data modeling
techniques for XML will become much more important with XQuery updates.

But this is not XML vs. relational, this is normalized vs. non-normalized.
XQuery updates will not magically normalize non-normalized data. SQL
updates don't either. Data modeling is a good thing, and normalized
representations of data are the best for persistent stores that need to be
normalized.

Jonathan