Re: comments on RIF BLD from OWL WG

Peter - thanks for the responses.

There will be another lag in responding to this as we are preparing for a F2F. 
FYI, we expect the next WDs in about a months time.  You can check the RIF home 
page (w3.org/2005/rules) where there are links to BLD and FLD working documents, 
but they are in a high state of flux right now - more stable versions will be 
ready for the F2F in two weeks.

-Chris

Peter F. Patel-Schneider wrote:
> Here is the response from the RIF WG to the OWL WG comments on the RIF
> BLD document.  
> 
> I expect to produce a personal response.  If the WG wants to respond as
> well, that would be fine.
> 
> 
> peter
> 
> 
> 
> 
> Peter,
> 
> Here are responses to your message "from the OWL WG" to RIF public comments on 
> Nov. 2.  Feel free to forward to the owl-wg, I cannot post to it.
> 
> 
>  > ** Comments on the Syntax
>  >
> 
>  > Why is the complex signature mechanism in this document, as the only
>  > used language doesn't really need it?
> 
> Signatures are part of the general framework of RIF from which other
> dialects are to be derived. This general framwork has meanwhile been split off
> of the dialect specification, resulting in the FLD document.
> 
>  > Further, the signature mechanism
>  > cannot capture the syntax of the BLD condition sublanguage, so it is not
>  > even adequate for distinguishing between dialects.
> 
> This question is quite unclear.  The signature mechanism is intended to be used
> for defining and extending RIF dialect semantics.  Can you be more specific?
> What do you mean by the inability to "capture" the syntax and why it is relevant?
> 
>  > Why are there are three different kinds of atomic formulae (regular,
>  > slotted, and frame)?  This could cause problems with OWL integration, as
>  > it is not obvious which kind of formulae should be used for integration
>  > with OWL.  In particular, frame formulae might be the target for OWL
>  > Full and regular formulae the target for OWL DL.
> 
> The three kinds of formulae are related formally and, in fact, we expect frames
> to provide a natural way to anchor the OWL integration work.  The others are present
> because the RIF framework is intended to capture all the major types of atomic
> formulas used in rule languages.
> 
>  >
>  > * Semantics of the RIF BLD Condition Sublanguage
>  >
>  > The semantics is only for the RIF BLD Condition Sublanguage, not the
>  > full RIF Condition Sublanguage.
> 
> At present we are specifying RIF-BLD.  Other dialects will be specified
> separately and in due time.  The "Condition Language" distinction will
> be removed in future drafts and the syntax & semantics merged into the
> apprpriate BLD sections.
> 
>  > * Comments on the Semantics
>  >
>  > The mappings for predicates are partial.  It seems that this means that
>  > the truth value of some formulae are thus undefined, but no account is
>  > taken of this in the later development of the semantics.
> 
> This has been fixed.
> 
>  > Why is a new treatment of data values needed?
> 
> The treatment is not new -- it is equivalent, but more uniform. It was chosen
> for its uniformity, since the same mechanism can be used other RIF needs:
> data types and other kinds of symbols (IRIs and local).
> 
>  > Why does the set of known
>  > data types not include XSD data types like xsd:short?
> 
> It was decided to start with a subset of the data types.  There is no
> technical reason to exclude xsd:short and others. They might be included in
> the future.  It is also not clear why an exchange language needs to support
> all the XML data types.
> 
> 
>  >
>  > Why does there need to be a symbol space for IRI identifiers?  This may
>  > cause problems with OWL integration.
> 
> 
> This symbol space corresponds to RDF's resources. Which problem can it cause for 
> OWL?
> 
>  >
>  > The treatment of slotted formulae is unusual in that the predicates have
>  > a direct map to their extension but the slot names are first mapped into
>  > the domain.  This means that a=b implies that f[a->3] is equivalent to
>  > f[b->3].
> 
> In what sense is it "unusual"? It is usual in F-logic, but can be prevented by 
> signatures (in dialects).
> To be elaborated upon in the followup draft.
> 
> 
>  > * General Comments on the Condition Language
>  >
>  > The language is very complex.  It appears to have been designed to
>  > mirror several other languages.  In particular, the frame formulae
>  > appear to have been designed to mirror F-logic.
>  >
>  > The logic is not like RDF, as it is monomorphic and predicates are not
>  > first mapped into domain elements.
> 
> This is intended to be changed in the next draft.
> 
>  >  The frame part of the logic is not
>  > like regular frames, as the slot names are first mapped into domain
>  > elements.
> 
> 
> What is a "regular" frame?
> 
>  > * Notes on RIF-RDF compatability
>  >
>  > Why worry about interpretations where IP is not a subset of IR?  This
>  > only happens in simple entailment.  As there are already datatypes in
>  > RIF why not just go to datatype-entailment?
> 
> It is at the moment not clear which entailment regime(s) will be useful for RIF. 
>   It might be the case that we decide to use only D-entailment.  See also the 
> second last paragraph in the 
> [http://www.w3.org/TR/2007/WD-rif-rdf-owl-20071030/#Overview introduction].
> 
> 
>  >
>  > The treatment of ill-typed literals appears to allow accidental capture
>  > if the replacement IRI also occurs in the RDF graph.  For example,
>  >    "abc"^^xsd:decimal ex:a ex:b .
>  > RIF-RDF entails
>  > 
> http://www.w3.org/2005/rif/rdf-ill-typed-literal/uri-encode("abc"^^xsd:decimal)
>  >    ex:a ex:b .
> 
> There was already general skepticism in the working group about using such an 
> IRI encoding of ill-typed literals.  It was decided to remove this encoding, so 
> that it is no longer possible to directly use ill-typed literals in RIF rules.
> See also the example in 
> [http://www.w3.org/TR/2007/WD-rif-rdf-owl-20071030/#RDF-Compatibility section 2].
> 
> Note that it is, however, not the case that RIF-RDF entailment matches RDF 
> D-entailment when the set of rules is empty; see the example at the bottom of 
> [http://www.w3.org/TR/2007/WD-rif-rdf-owl-20071030/#head-7bc418db41931aa0bec2cdadef81be12759c6807 
> section 2.2.1.2].
> 
> 
>  >
>  > Note that rdf:type is not related to membership formulae (i#c) and
>  > rdfs:subClassOf is not related to subclass formulae (c1##c2).  This does
>  > not seem to be reasonable.
> 
> In the [http://www.w3.org/TR/2007/WD-rif-rdf-owl-20071030/ current draft] they 
> are related; see 
> [http://www.w3.org/TR/2007/WD-rif-rdf-owl-20071030/#head-0d9bc055f4ca271102e7b53420888f3818628265 
> section 2.2.1.2.1].
> 
> 
>  >
>  > * RIF-OWL Compatability
>  >
>  > There was a section on RIF-OWL compatability in an earlier draft of the
>  > document but it has been removed.
>  >
>  > * Notes on RIF-OWL Compatability.
>  >
>  > There is a question as to which part of the syntax OWL should map to.
>  > There is also a question as to whether OWL syntax should map to RIF
>  > facts.
> 
> The questions will be addressed by the recently established OWL-RIF taskforce.
> 
> 
> 

-- 
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, 4 February 2008 03:57:34 UTC