# Re: [SWC] Action-830

From: Chris Welty <cawelty@gmail.com>
Date: Sun, 07 Jun 2009 22:58:59 -0400
Message-ID: <4A2C7E73.2020301@gmail.com>
To: Axel Polleres <axel.polleres@deri.org>
CC: Jos de Bruijn <debruijn@inf.unibz.it>, "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>

Axel, Jos, &al,

I updated SWC to be more consistent with the newer defintion of semantic
multi-structures.  I saw that Jos was using the bold-italic I ('''''I'''''') to
denote the "common elements" of the mappings in the structures within the
multi-structure (ie everything except local constants), which was kind of a
shortcut to minimize the changes to SWC introduced by multi-structures, but
Michael's new definition provided just such a shortcut with, conveniently, the
same name ('''''I'''''') - which is the environment or context for interpreting
document formulae.  So I just made the text a little more consistent and removed
the text that explained Jos' use of ('''''I''''''), since they are now the same.

Take a look.  I believe this closes the last loose end on SWC.

-Chris

Axel Polleres wrote:
> * I am fine to keep the DL-safeness definitition "as is" for LC.
> * I guess the point on the semicolon in the definition of
>   multistructures requires Michael Kifer's response.
>
> Axel
>
> Jos de Bruijn wrote:
>>
>> Axel Polleres wrote:
>>> find my comments inline below. This completes ACION-830
>>> http://www.w3.org/2005/rules/wg/track/actions/830
>>>
>>> Overall, I am fine with most of the changes made wrt.
>>> Urgent open points:
>>>
>>>  - DL-safeness definition.
>>>
>>>  - Semantic multistructures and dl-multi-structures still look
>>> inconsistent.
>>>
>>>
>>
>>
>> My responses in-line.
>>
>>>>> Section 3.1
>>>>> ===========
>>>>>
>>>>> * Section 3.1.2 "A RIF-RDF combination consists of a RIF document and
>>>>> zero or more RDFgraphs"
>>>>>
>>>>> Why do we allow only 1 RIF dcoument and arbitrary RDF graphs in a
>>>>> combination?
>>>> Because an RIF document an import any number of RDF graphs.
>>>
>>>
>>> I am not sure whether I understand this reply, but what I
>>> asked was why not several RIF documents can be involved, but ...
>>
>> Section 5 says how to interpret an RIF document importing a number of
>> RDF graphs. There is only one RIF document involved here, and so there
>> is no point to define the semantics for combinations involving more than
>> one RIF document.
>>
>>>>> This means that simple entailment in combination with an empty
>>>>> ruleset is not the same as simple entailment in RDF... I think that
>>>>> should be pointed out explicitly. It would be also worthwhile to add
>>>>> this example,
>>>>> i.e. I suggest to add (at the end of Section 3.2.3):
>>>>> "Note that simple entailment in combination with an empty ruleset is
>>>>> not the same as simple entailment in RDF, since certain entailments
>>>>> regarding datatypes are enforced by the RIF-BLD semantics in
>>>>> combinations. For instance, given two graphs
>>>>>
>>>>>  G1= { :s :p "foo" .} and
>>>>>  G2= { :s :p "foo"^^xs:string }
>>>>>
>>>>> as well as an empty RIF document R.
>>>>>
>>>>>  G1 |=/=_simpleRDF G2
>>>>> entailment] , but
>>>>>
>>>>>  <R,{G1}> |=_simple <R,{G2}>
>>>>> "
>>>> There is already an example to this effect in the introduction to
>>>> section 3.
>>>
>>> Then at least a pointer would be worthwhile here, so a short version
>>>
>>> "Note that simple entailment in combination with an empty ruleset
>>>  is not the same as simple entailment in RDF, since certain entailments
>>>  regarding datatypes are enforced by the RIF-BLD semantics in
>>>  combinations, cf. also Example [pointer-to-example] before."
>>
>> done
>>
>>>>> Section 4:
>>>>> ==========
>>>>>
>>>>>
>>>>> * Section 4.1.1
>>>>> "Given a set of OWL 2 DL ontologies O, a variable ?x in a RIF rule Q H
>>>>> :- B is DL-safe if it occurs in an atomic formula in B that is not of
>>>>> the form s[P -> o] or s[rdf:type -> A], where P or A occurs in one of
>>>>> the ontologies in O."
>>>>>
>>>>> That doesn't seem to be sufficient, take:
>>>>>
>>>>> ?X [rdf:type -> d ] :- Or ( ?X [rdf:type -> c ] p(?X) )
>>>>>
>>>>> this is DL-safe according to the definition above but can be expanded
>>>>> to two rule one of which wouldn't be DL-safe.
>>>>>
>>>>> Rather, we need to adopt a safeness notion similar to Core.
>>>> You are right. The definition is not sufficient. For now I just defined
>>>> it for disjunction-free rules. I hope I will be able to include a
>>>> proper
>>>> safeness condition later on. You can also have a go at it, if you feel
>>>> like it.
>>> Didn't manage to tackle it either, and will likely not be able this
>>> week, sorry.
>>
>> Do you think it is critical to have the refined definition in place
>> before LC? I think it is OK to refine the definition later, since it is
>>
>>>>> * Section 4.2.2.1
>>>>>
>>>>>
>>>>> *
>>>>> Definition (dl-semantic multi-structure):
>>>>> "I<sub>1C</sub>, ..., I<sub>1C</sub>"
>>>>>
>>>>> looks weird, better use 1...n as superscripts as in
>>>>> http://www.w3.org/2005/rules/wiki/BLD#def-bld-semantic-multistruct
>>>>>
>>>>> Again, shouldn't we use \hat{I} rather than I for
>>>>> multi-structures as in BLD to be consistent?
>>>>>
>>>>> *
>>>>> same definition:
>>>>> Bullet 1 ends with "and ; "
>>>>> That looks incomplete, is there anything missing?
>>>>>
>>>>> *
>>>>> "I(&phi;), for any other formula or symbol &phi;, and the truth
>>>>> valuation
>>>>> function TValI are defined as in BLD semantic structures. "
>>>>>
>>>>> I am, honestly, getting confused with the definitions of
>>>>> multi-structures in BLD vs. SWC.
>>>>>
>>>>> dl-multistructures consist of {I_1, ..., I_n}
>>>>> whereas BLD multistructures are {J,I; I_i1, I_i2, ...}
>>>>> so, I am unsure what "defined as in BLD semantic structures."
>>>>> means to say.
>>>>>
>>>>> (BTW: I sent an amendment to my BLD review  per mail in this regard
>>>>> as well)
>>>> I updated the definition in SWC to reflect the changes in the
>>>> definition
>>>> in BLD. Please have a look.
>>>
>>>  - semantic multistructures and dl-multi0-structures still look
>>> inconsistent:
>>>
>>> section 4.2.2.1
>>>
>>>
>>> "
>>> Formally, a dl-semantic multi-structure Î is a set of dl-semantic
>>> structures {J,I, Ii1, Ii2, ...}, where "
>>>
>>> misses th ";" used in BLD... shouldn't this be:
>>>
>>> "Formally, a dl-semantic multi-structure Î is a set of dl-semantic
>>> structures {J,I; Ii1, Ii2, ...}, where "
>>>
>>> ?
>>
>> To be honest, I don't understand the ';'. It is a set, and the ',' is
>> commonly used to separate the individual elements in a set.
>>
>>>
>>>  - same here:
>>>
>>> "Given a dl-semantic multi-structure Î={I1, I2, ...}, "
>>>
>>> should be:
>>>
>>> "Given a dl-semantic multi-structure Î={{J,I; Ii1, Ii2, ...}, "
>>
>> It is a set of structures, so it does not really matter which symbols I
>> use for the individual elements.
>>
>>
>> Cheers, Jos
>>
>
>

--
Dr. Christopher A. Welty                    IBM Watson Research Center
+1.914.784.7055                             19 Skyline Dr.
cawelty@gmail.com                           Hawthorne, NY 10532
http://www.research.ibm.com/people/w/welty

Received on Monday, 8 June 2009 02:59:51 GMT

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