Suggestions for implementing a "document matches" program?

Hi Folks,

Suppose that you want to create a PROGRAM which, when handed *any* XML
instance document, decides whether or not it meets this desire:

"I am interested in purchasing a camera with a 75-300mm zoom lens, that
has an aperture of 4.5-5.6, and a shutter speed that ranges from 1/500
sec. to 1.0 sec."

To recap, here's the scenario:

XML instance document --> PROGRAM ---> "Yes! It's a match!" 
                                       (or, "No match")

[The idea is that PROGRAM will "consult" the Camera Ontology whenever it
encounters XML elements that it does not "understand"]

What are your recommendations for implementing PROGRAM?

Would you recommend using a query language, such as DQL (DAML Query
Language) combined with some Java code?  Or would you recommend using
something else?  Has someone already done something like this?  /Roger