enrique said:
I've not looked under the hood of an XML document archive, but from my
casual reading and my working indirectly with with them:
* they are not relational databases
* they do not have support for SQL; "querying" capability is probably
limited to what the vendor provides in a proprietary API
Leaving aside the confusing issue of what "an archive" actually is,
I think your second point is unlikely: I would expect any current
XML storage system that has a search capability to use one of the
many XML search engines and provide an interface using XQuery. I
can't think of any good reason why "an XML document archive" would
need SQL support.
It is a mistake to expect to be able to use SQL to search information
which may not be meaningfully put into relational form. If you are
dealing exclusively with e-commerce data, where your XML is just a
verbose representation of traditional rectangular data (rows and cols)
then it is possible to map the features of SQL onto a relational
data model. But I contend that if your XML information is traditional
text documents, a relational model is probably not as useful as the
structural access provided in (for example) XSLT by XPath, and the
query access provided by XQuery.
[OP]
I'm trying to understand the differences between a XML document archive
versus a relational data base.
An XML document archive is for storing XML documents.
A relational database is for storing relational data.
If your XML documents can be normalised to the relational model, or
if your relational data can be expressed adequately in XML, feel free
to use either system, otherwise pick the right tool for the job.
///Peter
