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From mark harwood <markharw...@yahoo.co.uk>
Subject Re: "Advanced" query language
Date Fri, 23 Dec 2005 12:34:59 GMT
I suspect it's a little too ambitious to provide a
unifying common abstraction which wraps event based
*and* "pull" parser approaches. 

I'm personally happier to stick with one approach,
preferably with an existing, standardized interface
which lets me switch implementations. I didn't really
want to have to design a general API for parsing XML
as part of this project. 

It feels like we should probably try to define parser
scope a little more clearly at this stage before
diving into implementation details.
As an example, I was running a config last night that
let me do this:
<QueryTest>
  <Index type="RAM">
    <Document>
      <Field name="title">My report 1</Field>
    </Document>
    <Document>
      <Field name="title">My report 2</Field>
    </Document>
   <Index>
   <Query>
      <BooleanQuery>
      .....
      </BooleanQuery>
   </Query>
   <ExpectedResults docs="1,2"/>
</QueryTest>
The parser framework was (apart from an annoying bug)
letting me construct and run this collection of
objects to create a RAMIndex , populate it, run
queries and test results.

In this scenario the parser is used as a generic
instantiator of different objects using configurable
choice of ObjectBuilders. That's why I used
"ObjectBuilder" as the building block not just
"QueryBuilder".

Maybe this is overstepping the mark but it certainly
seemed useful. I would be interested to confirm the
scope a little more.

ie should we offer:
1)  XML Parser implementation independence (via SAX,
DOM, other interface?) 
2) Pluggable choice of builders 
3) Support for builders to produce *any* object
construction (not just queries/filters)?
4) Ability for Queries to write to XML (choice of
parser configs can be used to write Query/Filter
objects as well as read them?)
5) Ability for Parser configurations to
"self-document" the XML structures they are capable of
parsing? ie produce a schema

There's a lot of ground that *could* be covered so it
would be good to get some concensus on where we might
be heading.









		
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