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Date: Tue, 19 Mar 2002 08:26:45 +0200
From: "Derek Hohls" <dhohls@csir.co.za>
To: <gcling@telocity.com>, <cocoon-users@xml.apache.org>
Subject: RE: XML for describing databases?
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Glenn

I would definitely be interested in this - tho' I am not sure that I
fully understand the approach you have taken eg. " submit
queries using that format"?

I am also curious as to how you format your output to make it 
human-readable if you do not use XSLT?

Cheers
Derek

>>> gcling@telocity.com 18/03/2002 05:38:08 >>>
I have been working on a similar problem but approaching it in a
slightly different way. I have taken more of an object-relational
mapping approach similar to products such as TopLink. Using this
approach you define your database schema and your XML result schema
separately and then map them together. For instance, the SQL tables
for
Employees (i.e. Employee, Department, Person) will be mapped directly
to
your resulting XML document and that document can be structured like:
            <department>
                        <name>accounting</name>
                        <employee>
                                    <firstName>John</firstName>
                                    <lastName>Doe</lastName>
                                    <employeeId>1234</employeeId>
                        </employee>
                        <employee>
                                    .
                        </employee>
            </department>
 
or it could be structured like:
            <employee deptName="accounting" id="1234">
                        <firstName>John</firstName>
                        <lastName>Doe</lastName>
            </employee>
 
or any other variation.
 
The mapping (created against a defined mapping schema as an XML
document) provides the information that is needed to build the queries
and create the resulting documents. XSLT is not used and the typical
result type from an XML query (<table name="department"><row><column
name="deptId">360</column>.</row>.</table><table>.</table>) is not
used.
The query is truly symmetric. You can define the result format, submit
queries using that format, and receive responses in that format. To
qualify your query you include the known data elements and the query
will be built to find those.
 
I have been working on this independently and would be interested in
comments. I currently have the query definition, submit, and response
working for moderately complex data sets (involving many-to-many
relations that can be brought to multiple places in the XML document)
and will work on defining insert and update as well.
 
- Glenn
 

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