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Michael Kay wrote:
>I wonder whether this is a wise way of using XML. Even with XML databases,
>most databases are optimized to handle large numbers of small/medium
documents
>rather than a single gigantic one. I don't think that using an XML document
as
>a replacement for a database is a particularly good idea. It's not the job
it
>was designed for.
Michael Kay also wrote:
>What I would really like to see is an XML database that gets rid of the
>concept of "document" entirely. But we're a long way from that at the
>moment. In all the systems I've seen, the choice of "what is a document"
has
>a profound effect on both the physical and logical design, and as a general
>rule of thumb, many small documents works better than a few large ones.
Sedna is designed to be optimized for both use-cases: (1) large numbers of
small documents (2) single gigantic one. As concerns physical Sedna design,
it works as follows. XML documents loaded in one collection in a Sedna
database are stored internally in as a single piece of data with a single
descriptive scheme (i.e. scheme that is derived from XML documents loaded).
To navigate during query processing inside the piece efficiently, nodes of
the all XML documents are clustered according to their positions in the
descriptive schema. So from the physical viewpoint it does not matter
whether it is a number of documents or a single large one. By the way,
experiments for XML data of various sizes, the results of which are
published at
(http://www.modis.ispras.ru/Development/Benchmarks/sedna_xmark_benchmark.htm
), were conducted with a single XML document.
Maxim Grinev
the Sedna team
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