Re: Friendly amendment to rif:subClassOf

<snip/>

>> rif:subclassOf is not a new concept. It is there in
>> every standard OO language. Jos' arg was that it is a new word in the
>> vocabulary, and Dave was questioning whether RIF should define such a
>> concept (incl. rdfs:subclassOf) in the first place.
> 
> I'm just hoping it makes what you proposed a little more palatable. But
> let's see - Dave and Jos?  Does Michael need still more coffee or do I?

My argument was that there are already semantic Web languages for
defining ontologies (including the subclass relation), so that RIF
should probably not invent a new vocabulary for defining ontologies (or
classifications), but rather show how existing vocabularies for ontology
definition (including (subsets of) RDFS) can be combined with the RIF.

Chris' proposal (rif:subclass rdfs:subproperty rdfs:subclass; use
rdf:type for instance statements?) seems to extend the RDFS vocabulary,
rather than creating a new vocabulary.
This could be a possible way to go for exchanging data models which do
not have reflexive subclass statements; however, I am not 100% convinced
that we need this extension.

I guess an important question is really whether people want to use
several different data models in the same RIF rule set.


Best, Jos


> 
> -Chris
> 
>>> Intuitively, it seemed to me that every rif:subclass relation is an
>>> rdfs:subclass relation, but there may be rdfs:subclass relations that
>>> a translator will not want to consider as rif:subclass (e.g. the
>>> reflexive cases, the cases where one of the arguments is not a class,
>>> the case where one of the arguments is a piece of rdf or rif syntax,
>>> etc).
>>>
>>> I guess it depends on whether you want every rdfs:subclass relation
>>> (including the entailed ones) in rdf graphs to entail rif:subclass in
>>> RIF rules or whether you want a translator to do it.  I could go
>>> either way.
>>>
>>> Note that rif:subclass rdfs:subproperty rdfs:subclass does not make
>>> rif:subclass reflexive - it does mean that for every A rif:subclass B
>>> we would also have A rdfs:subclass A and B rdfs:subclass B, but
>>> that's just what rdfs:subclass means.  Shouldn't be a problem for
>>> rif:subclass.
>>>
>>> <chair>
>>>
>>>>
>>>>     --michael 
>>>>
>>>>> </chair>
>>>>> Here is a hopefully friendly amendment to the proposal to add a
>>>>> rif:subClassOf relation to BLD:
>>>>>
>>>>> If we just say that <rif:subClassOf rdfs:subPropertyOf
>>>>> rdfs:subClassOf> I think it goes part of the way in addressing the
>>>>> chief concern of Jos and Dave (which is, as I understand it, that
>>>>> we shouldn't add yet another subclass relation to the semantic web).
>>>>>
>>>>> This would make it clear that we are not really creating something
>>>>> new, just imposing a restriction on something already there - in
>>>>> particular all rif:subClassOf relations are also rdfs:subClassOf
>>>>> relations, but not the reverse, and we would say that
>>>>> rif:subClassOf is not reflexive, only holds between classes, etc.
>>>>>
>>>>> Less the new name, this is what Jos proposed - to define a suitably
>>>>> restricted subset of RDFS that would be usable for RIF.  I think
>>>>> the new name (rif:subClassOf) helps to make it clear that we do not
>>>>> intend the full rdfs semantics, rather than "hiding" that in the
>>>>> semantics.
>>>>>
>>>>> <chair>
>>>>>
>>>>> -Chris
>>>>>
>>>>> Chris Welty wrote:
>>>>>> Michael Kifer wrote:
>>>>>>> Rumblings on why we need classification terms in RIF
>>>>>>> (and why RDF's vocab should not be used)
>>>>>>> ===================================================
>>>>>>>
>>>>>>> Two issues: whether we should define facilities for expressing
>>>>>>> some data
>>>>>>> model stuff and whether we should use rdfs for this.
>>>>>>>
>>>>>>> Rationale:
>>>>>>>    If we do not have such constructs then everybody will be
>>>>>>> inventing their
>>>>>>>    own. People will not be able to specify any part of their data
>>>>>>> model in RIF
>>>>>>>    which will reduce the usefulness of RIF as an exchange language.
>>>>>>>
>>>>>>> Why it is not good to use RDF's facilities to define class
>>>>>>> hierarchies.:
>>>>>>>    RDF is a foreign language whose semantics is burdened with
>>>>>>> non-standard
>>>>>>>    things. For instance, subclass is reflexive.
>>>>>>>
>>>>>>>    This is bad because not every language out there uses
>>>>>>> reflexive subclasses.
>>>>>>>    For instance, if we map, say, FLORA-2's subclass relationship
>>>>>>> to RDFS's then
>>>>>>>    in the translation (RIF) the query whether foo is a subclass
>>>>>>> of foo will
>>>>>>>    say "yes" but in FLORA-2 it will say "no".
>>>>>> </chair>
>>>>>> No, no - translating flora2:subclass into rdfs:subclass would be
>>>>>> incorrect, because they have different semantics.  For me, this is
>>>>>> the stronger point in favor of rif:subclass - since so few systems
>>>>>> use the rdfs semantics for subclass, very few systems when
>>>>>> translating into RIF would use it in their translations.
>>>>>>
>>>>>> Same for below.  You shouldn't translate ilog:subclass into
>>>>>> rdfs:subclass.  So, in fact, as far as we know, only rdfs based
>>>>>> systems would ever use rdfs:subclass when translating through rif,
>>>>>> and everyone else would have to invent their own.
>>>>>> <chair>
>>>>>>
>>>>>>>    Let's look at some other examples, like ILOG. From my limited
>>>>>>> experience
>>>>>>>    with it, I remember that it uses Java as its data model. So,
>>>>>>> suppose
>>>>>>>    there is a class foo in ILOG, which comes from Java. An ILOG
>>>>>>> set of
>>>>>>>    rules must not derive "foo sub foo" because this is not true
>>>>>>> in the data
>>>>>>>    model. However, it we translate Java subclass relationship into
>>>>>>>    rdfs:subclassOf then the resulting RIF translation should
>>>>>>> generate "foo
>>>>>>>    sub foo". (In truth, as I recall, ILOG does not have "sub" in
>>>>>>> the heads
>>>>>>>    of the rules, but it is easy to imagine that next year ILOG is
>>>>>>> extended
>>>>>>>    with something like a query facility. Then their stock will
>>>>>>> plummet
>>>>>>>    because their rule sets will not be faithfully exchangeable
>>>>>>> through RIF
>>>>>>>    :-)
>>>>>>
>>>>> -- 
>>>>> 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
>>>>>
>>>>>
>>>>
>>>>
>>> -- 
>>> 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
>>>
>>>
>>
>>
>>
> 

-- 
Jos de Bruijn            debruijn@inf.unibz.it
                      http://www.debruijn.net/
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