[Versa] Issue 3

[Michael Olson]

>>
>> What I don't like about this approach is that if all you want is the
>> objects, conceptually, and until we get a good optimizer, you get the
>> statements (lots of data) just to trim it back to objects.....
>
> Well, there is a lot in Versa which needs a decent optimizer, which is
> why I wrote one for 4RDF.  I could fairly easily extend the optimizer  
> to
> this case.
>
> The requires-good-optimizer characteristic is pretty standard in query
> language.  The more expressive the language, the more work needs to be
> done in an optimizer.
>

I agree with the above.  However, even the process of (parser -->  
optimizer --> results) will be slower then (parser --> results).

I guess what I am saying is it is:

*very* common to use traverse
*almost as very* common to use filter
*far* less common to need the statement.  After all, you probably  
specify 2 of the three parameters in the filter so you know the  
statement
*hardly* common to get just the predicates.


One thing to note for implementation, in the Rigel simple query  
language, I found that I could get rid of a lot of other functions by  
having a core query like the one above.  Example, properties() can go  
away because it is support by the query.  If not go away, then a query  
modifier can be put in place to translate all "properties()" called  
into predicate(traversal expression).

Mike

>
> --  
> Uche Ogbuji                               Fourthought, Inc.
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> Use CSS to display XML, part 2 -  
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> XML Output with 4Suite & Amara -  
> http://www.xml.com/pub/a/2005/04/20/py-xml.html
> Use XSLT to prepare XML for import into OpenOffice Calc -  
> http://www.ibm.com/developerworks/xml/library/x-oocalc/
> Schema standardization for top-down semantic transparency -  
> http://www-128.ibm.com/developerworks/xml/library/x-think31.html
>
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------------------------------------------------------------------------ 
-----------------
Mike Olson                                                Principal  
Consultant
mike.olson at fourthought.com                +1 720 253 4662
Fourthought, Inc.                                       
http://Fourthought.com
PO Box 270590,                                       http://4Suite.org
Louisville, CO 80027-5009, USA
XML strategy, XML tools, knowledge management