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Re: property paths three more test cases pp13, pp14, pp15

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Tue, 21 Dec 2010 11:20:44 +0000
Message-ID: <4D108D8C.8000907@epimorphics.com>
To: Steve Harris <steve.harris@garlik.com>
CC: Axel Polleres <axel.polleres@deri.org>, SPARQL Working Group <public-rdf-dawg@w3.org>


On 21/12/10 11:12, Steve Harris wrote:
> On 2010-12-20, at 17:23, Axel Polleres wrote:
>
>> Steve,
>>
>> I added a new use case pp16 along the lines you suggest, see details below.
>>
>> On 20 Dec 2010, at 16:46, Steve Harris wrote:
>>
>>> I think pp14 would be more enlightening if the pp14.ttl included a disconnected foaf:knows graph, and some triples using another predicate. Something like:
>>>
>>> @prefix :<http://example.org/>  .
>>> @prefix foaf:<http://xmlns.com/foaf/0.1/>  .
>>>
>>> :a foaf:knows :b .
>>> :b foaf:knows :c .
>>> :d foaf:knows :e .
>>> :f foaf:name "test" .
>>> :a foaf:homepage :h .
>>>
>>> Even after Axel's proposed changes I find the wording a bit impenetrable, though admittedly I haven't had time to study the algebra.
>>>
>>> Axel, can you tell mw what results you'd expect from pp14.rq with that data?
>>>
>>
>> your data returns, according to my understanding of the algebra:
>>
>> -------------------
>> | X      | Y      |
>> ===================
>> | :a     | :a     |
>> | :a     | :b     |
>> | :a     | :c     |
>> | :b     | :b     |
>> | :b     | :c     |
>> | :c     | :c     |
>> | :d     | :d     |
>> | :d     | :e     |
>> | :e     | :e     |
>> | :f     | :f     |
>> | :h     | :h     |
>> | "test" | "test" |
>> -------------------
>
> OK, thanks. Intuitively I find the :e/:e, :f, :h, and "test" results odd, but I've not given enough time to trying to understand the usecases.

One example is:

    ?x rdf:type/rdfs:subClassOf* ?T

which is

    ?x rdf:type ?Z
    ?Z rdfs:subClassOf* ?T

Under RDFS:

   <C> rdfs:subClassOf <C>

If you are writing that over plain data, you need "a rdfs:subClassOf* a" 
(the {0} case) to get the subclass effect or a more complex query.

	Andy
Received on Tuesday, 21 December 2010 11:21:23 GMT

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