[Versa] Versa issue: drawing the line on entailments

[Michael Olson]

On Aug 12, 2005, at 10:20 PM, Chimezie Ogbuji wrote:

> True.  I think the specification should *encourage* inferencing and
> suggest where it can be done, but be clear not to make it a requiment.
>  Though I think the language as it is currently doesn't make it a
> requirement:
>
> type(resource)
>
> Returns a list of all resources of a specified type, as defined by
> RDFS and optionally DAML schema specifications..

In my mind, I think we need to leave off the last little bit.

a)  what id DAML is not supported?
b)  what if OWL if supported?
c)  what is some new funky technology is supported?

I think it is best to just say "what ever the underlying model"  
considers as all of the resources of the specified type.

>
> traverse(...) - regarding vtrav:transitive
>
> ... If omitted, no transitivity is applied except any applied by the
> underlying model (e.g. if rdf:type statements are traversed, or
> statements marked as daml:transitiveProperty). ...
>

or subClassOf given rdfs8, or subPropertyOf given rdfs5 etc.


Again, I think it is best to say something like

"with out the transitive flag, versa will return all direct objects of  
the statemtne {resource}, {property}, *.

If the transitive flag is specified, then the versa implementation will  
attempt to perform the transitive completion of the property and return  
the computed set.  It should be noted that

a)  this will take longer
b)  if this is performed on a property that the model already considers  
transitive then the results will grown exponentially"




>
>
>> We should have a proper answer to this in the spec.  Right now  
>> 4Suite's
>> implementation does rdf:type inferencing, as he says, but I've always
>> been willing to separate the query language from such matters.  My
>> suggestion is that we state that Versa does not require any entailment
>> within an RDF model, but that a back end is free to do so.  Sure this
>> means that Versa results can different between back ends, but I think
>> that what inferences an implementation handles for the user is a
>> separate issue to document.
>>

I agree 100%.  There is an up and down side.  Some models may return  
more results.  Some models will return less results more quickly.

Leave it up to the user. ...

Mike

>>
>> --
>> Uche Ogbuji                               Fourthought, Inc.
>> http://uche.ogbuji.net                    http://fourthought.com
>> http://copia.ogbuji.net                   http://4Suite.org
>> Use CSS to display XML, part 2 -  
>> http://www-128.ibm.com/developerworks/edu/x-dw-x-xmlcss2-i.html
>> 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  
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Fourthought, Inc.                                       
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