xml-dev - Re: ANN: XML and Databases article

["Ken North" <ken_north@compuserve.com>]

Re: ANN: XML and Databases article

Ingo Macherius wrote
> The other problem is you can store XML, but
> have to explicitely model relations (parent, sibling, child, ... and
> all other axis you need) by foreign keys. The number of "metatables"
> with structural information quickly outnumbers the useful data. Again
> we tried, benched and canceled.

This reads like you always decomposed or mapped XML documents to store them,
as opposed to storing some XML documents as a single column. The choice of
how to store documents in a database will vary on a case-by-case basis,
depending on application needs.

The critical factor is whether you simply need a document store, or you are
dealing with data that needs to be used in queries, particularly "rich"
queries:

(find something in XML documents and search geospatial data to retrieve the
nearest location).

If your XML is in a separate document store, you are faced with using data
integration middleware and marshaling data. From your comments about
performance, my guess is that you weren't running this type of mixed query
but were focusing on simply retrieving XML.

> The number of "metatables" with structural information quickly outnumbers
the useful data.

That's an accepted behavior in the OLAP world -- even more so now that disk
and memory are inexpensive.

> Currently we are investigating our PDOM, which just maps between a
> W3C-DOM and persistent streams of serialized Java objects (paper will
> be at OOPSLA99). Instead of modeling structure we try to scale by
> means of intelligent, specialized cache strategies.

That sounds like a promising solution for Java development.




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