Hi All,
I'm going round in circles trying to think of the 'best' way to implement a data
server. This data server will be accessed by several systems, some in operation, some
'on the drawing board' and some that haven't even been thought of yet.
Probably the best performing solution would be to write all application queries as
stored procedures, but that has the obvious and major disadvantage of tightly coupling
the data server with its client applications.
What I would like to do is to 'publish' the type of data that is available e.g via an
XML schema, and then allow the client applications specify what data fields they
require and what the 'selection' criteria is.
Let me give an example to clarify:
Suppose I have a DB that contains a list of people and addresses. Each person can have
0 or more addresses (home, office, mailing, etc) and each address can be 'used' by 0
or more people.
Now suppose I have a HR application that wants to list all the addresses for a
specific person. It would want to pass the data server a 'person id' and have it
return something along the lines of:
<person>
<pid>1001</pid>
<name>Joe Bloggs</name>
<address type='home'>
<aid>1234</aid>
<line1>Bloggsville</line1>
</address>
<address type='office'>
<aid>1235</aid>
<line1>The Slave Pit</line1>
</address>
</person>
Finally suppose I also have a mailing application that wants list all the people who
have the same 'office' address. It would want to pass the data server an 'address id'
and have it return something like:
<address>
<aid>1235</aid>
<line1>The Slave Pit</line1>
<person>
<pid>1001</pid>
<name>Joe Bloggs</name>
</person>
</address>
The crux of the problem seems to centre around mapping the DB relations to the
hierarchical structure of XML. In the above example the 2 client applications model
the relationship between address and person differently.
I have looked at using annotated schemas with XPath but the main problem with that
solution is a single annotated schema is unlikely to be sufficient for all (or even
one) client applications. When a new client application comes along I will almost
certainly need to create a new schema. The more schemas that are produced the closer I
am to the specific stored procedure solution. The example above would require two
XSDs, one for each application.
Does anyone have any ideas or pointers to resources that can help me out? Is this
actually possible or do I just have to accept a certain level of inter-application
dependency.
Many thanks in advance,
Phil Ruelle
Website: http://www.mourant.com
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