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Re: accessingCollections: postpone due to lack of design/implementation experience?

From: <jos.deroo@agfa.com>
Date: Tue, 1 Feb 2005 12:34:42 +0100
To: andy.seaborne@hp.com
Cc: connolly@w3.org, RDF Data Access Working Group <public-rdf-dawg@w3.org>, public-rdf-dawg-request@w3.org
Message-ID: <OF9AA30C46.A0B88AC0-ONC1256F9B.0039FD81-C1256F9B.003F9A19@agfa.com>

Andy,

In our implementation experience o:item triples
are inferred triples constrained by

{?S rdf:first ?X} => {?S o:item ?X}.
{?S rdf:rest ?B. ?B o:item ?X} => {?S o:item ?X}.

So it relates things to lists (for instance running
OWL test manifest we have 824 occurences of o:item)
and same items are indeed in all nested lists (or
eventually in other lists, as RHS could rebind).
I wished it was owl:item (as it is in DAML+OIL)..

Thus far I haven't found a motivationg test case
to use N3/Turtle collection ( ) notation in q:where
clauses of QL, but I do have many cases where ( )
is used in q:select clauses.

-- 
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/




"Seaborne, Andy" <andy.seaborne@hp.com>
Sent by: public-rdf-dawg-request@w3.org
01/02/2005 10:26
Please respond to andy.seaborne

 
        To:     Jos De_Roo/AMDUS/MOR/Agfa-NV/BE/BAYER@AGFA
        cc:     connolly@w3.org, RDF Data Access Working Group <public-rdf-dawg@w3.org>, 
public-rdf-dawg-request@w3.org
        Subject:        Re: accessingCollections: postpone due to lack of design/implementation 
experience?



Jos,

Nice example!  I couldn't be sure whether the property o:item relates a 
list
to its members or it relates an item to the intersection or union.

If it's the approach of an inferred triple, like rdfs:member except for
collections, relating list to member:

For ("x" "y")

_:b1      rdf:rest  _:b2 .
_:b1      rdf:first  "x" .

_:b2      rdf:rest  () .
_:b2      rdf:first  "y" .

isn't "y" is a member of two lists? the one starting a _:b1 and the one
starting at _:b2 because a tail of a list is itself a list.  Your example 
would 
work, I think, because it looses the duplicate solution sublist as ?L is 
the 
head of the whole list but other queries ("find all the lists and their 
members") will create unhelful solutions if o:item runs object to subject 
as 
well subject to object.

This approach doesn't geneate a requirement on SPARQL as far as I can see 
although nice syntax would be nice.  Do you think it has an impact on the 
query 
language?

If the former definition of o:item, relating intersection or union to its
members, then it is in the style of using additional information, over and
above that of the collection itself.  Again, I don't think it impacts the
SPARQL design other than possible syntax.  Do you see a requirement of 
SPARQL?

                 Andy


jos.deroo@agfa.com wrote:
> wait a minute..
> 
> here's a test case I was actually working on (and which is running right 

> now)
> 
> given 
> 
> [ :operator     :RXPelvisOfHipInjury;
>   :precondition [ owl:intersectionOf ( :ConfirmNonPregnancy 
> :PhysicalExamOfHipInjury ) ];
>   :action       [ owl:intersectionOf ( :CADMeasurement :Diagnosis ) ];
>   :effect       [ owl:unionOf ( :InsertHipBolt :ReplaceHip 
> :RevalidationOfHipContusion ) ] ].
> 
> then I would really like to see the query equivalent with
> 
> [] q:select {?X :andStep ?Y};
>    q:where  {?S :operator ?X; :effect ?A. ?A owl:intersectionOf ?L. ?L 
> o:item ?Y}.
> [] q:select {?X :orStep ?Y};
>    q:where  {?S :operator ?X; :effect ?A. ?A owl:unionOf ?L. ?L o:item 
> ?Y}.
> 
> returning
> 
> :RXPelvisOfHipInjury :orStep :InsertHipBolt. 
> :RXPelvisOfHipInjury :orStep :ReplaceHip. 
> :RXPelvisOfHipInjury :orStep :RevalidationOfHipContusion. 
> 

Dan Connolly wrote:
> While the lack of support for accessing collections has been
> noted in various places, we didn't identify it as a requirement
> (or even an objective) in http://www.w3.org/TR/rdf-dawg-uc/ .
> If anybody now thinks it's a v1 requirement, speak now or
> forever hold your peace.
> 
> It's also in order to share design ideas.
> 
> But assuming no lightbulbs go off in such a way as to
> gain consensus, due to lack of design/implementation experience
> I propose we postpone this issue.
> 
> http://www.w3.org/2001/sw/DataAccess/issues#accessingCollections
> 
Received on Tuesday, 1 February 2005 11:35:22 GMT

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