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From markharw00d <>
Subject Re: "Advanced" query language
Date Sat, 03 Dec 2005 01:42:03 GMT

>What ever is generating the xml could just as easily create/instantiate the query objects.
Yes, it is easier using the existing Java objects to construct queries 
but they are inappropriate when you consider the scenarios 1 to 3 I 
outlined earlier (query persistence, support for clients written in 
other languages or remote clients that don't want/need Lucene 
implementation classes locally). I find the separation of service 
request from service implementation is generally useful and using Query 
objects for both  feels a bit dodgy.

I was not necessarily considering this proposal as a query language 
which power end-users would normally  type. I saw this more as a syntax 
which would typically be generated by application code  and could be 
conveniently persisted and/or serialized between machines. For example, 
I've a nice applet based GUI query builder for constructing boolean 
logic(see "Modern Information Retrieval" p285) which accumulates the 
user's query clauses, constructs a regular Lucene query string and sends 
it serverside. Unfortunately, using this approach I cannot offer the 
full range of Lucene query capabilities because they can't all be 
expressed in the existing query syntax. Yes,I could create Query objects 
in the client applet and serialize them to the server but how do I save 
them in an audit log or database of "saved queries"?
I suspect there are many other Lucene applications which are essentially 
fronted by forms that are interpreted by application code to produce the 
query strings. In these scenarios where app code creates the query 
requests the "end-user-friendliness" of the query syntax may be a lesser 
priority compared to the required flexibility to represent all types of 
Lucene Queries - hence the XML suggestion, although I'm not married to that.

Yonik was right to highlight the parallel with  SQL here.

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