W3C home > Mailing lists > Public > public-rif-wg@w3.org > April 2008

RE: imports + metadata

From: Paul Vincent <pvincent@tibco.com>
Date: Thu, 10 Apr 2008 09:28:50 -0700
Message-ID: <8F4A4531BB49A74387A7C99C7D0B0E0503DD7FA7@NA-PA-VBE02.na.tibco.com>
To: "Jos de Bruijn" <debruijn@inf.unibz.it>, "Sandro Hawke" <sandro@w3.org>
Cc: <public-rif-wg@w3.org>

Added comments below...

Paul Vincent
TIBCO | Business Optimization | Business Rules & CEP
 

> -----Original Message-----
> On Behalf Of Jos de Bruijn
> 
> Sorry for being late on the imports issue.
> 
> Let me first respond to Sandro's ideas:
> 
> > 'import' of a RIF document would merge in the rules in that document
> 
> No contest here :-)

[PV>] Allow me. :) 
Are we talking about RIF, or BLD? I can see why this might be the case
in BLD, but other dialects (eg PRD) will likely have constraints (eg the
data schema used, signature of a service for a ruleset being
interchanged, etc) which means there will me much more work for a
translator. 

Now, if there is an assumption "RIF document = ruleset" and "any import
will be assumed to be set up to use compatible data references" then
this works fine...

> 
> > 'importMeta' of a RIF document would merge in the metadata and also
the
> >       triples which encode the syntactic structure (which we haven't
> >       standardized but we should, and Axel made a proposal [1]
> 
> about importing metadata I don't really have an opinion.  I'm fine
with
> it if people think it's useful.
> I am a little uneasy about importing the syntactic structure of a rule
> set. I'm afraid it will invite people to work on the (nasty) syntactic
> level, instead of the (nicer) semantic level.

[PV>] You've lost me there - surely one imports a document that has both
syntax and semantics?
 

> 
> > 'import' of an OWL XML file [2] or an RDF/XML-file which is an
> >       owl:Ontology would (conceptually merge in the OWL-DL axioms,
> >       ignoring all triples not playing a role in the ontology
> 
> As discussed in the last telephone conference, you have a slightly
> different intuition behind the combination than I do.  I would rather
> phrase it in the form of a "data source reference", but would not have
a
> big problem with "import".
> 
> We do have the issue here of deciding how to treat the RDF/XML file.
> Should we use RDF simple entailment/RDFS/OWL DL/OWL Full?
> existence of some owl:Ontology triple is not sufficient, because both
> OWL DL and OWL Full have that.
> 
[PV>] A typical PRD import could utilize the same XML schema for both
importer and imported rulesets. Otherwise the translator has a lot of
XPATH processing to do to convert between schemas, presumably...

> 
> > 'importMeta' of such a document would give you the triples (ie the
> >       triples which encode the syntactic structure of the ontology).
> >       I'm not sure how you say you want OWL-Full inference or RDFS
> >       inference or something -- I think you "import" rules which
> >       implement that inference, but the import is understood to be
> >       symbolic -- you're allowed to use your own equivalent
reasoner.
> 
> Importing the structure of an RDF/XML document seems like an RIF-RDF
> combination using simple entailment. So, I don't really see how this
> helps.
> I could imagine using this keyword to "import" annotation property
> values from an OWL ontology.  When talking about OWL DL, a keyword
like
> this could be used to say you want to take the semantics of annotation
> properties into account [1].
> 
> 
> 
> Now to come to my proposal for the semantics of RIF imports:
> 
> A set of RIF rulesets R is imports-closed if, for any IRI i in an
import
> directive in any rule set in R such that i identifies a ruleset r,
t(r)
> is included in R.
> Here, t(r) is obtained from r by replacing every constant with symbol
> space rif:local  with a new globally unique constant.
> 
> The definition of entailment for RIF rulesets extends to sets of RIF
> rulesets in the natural way.
 
[PV>] This looks generic enough to work for any dialect.
 
> 
> If this semantics is acceptable, we still need to decide whether we
use
> the "directives" mechanism, or whether we extend the syntax of RIF
with
> the "imports" statement.  I don't have a very strong opinion either
way.
> 
> 
> Now to come back to the issue of referring to/importing RDF/OWL:
> 
> We have two somewhat orthogonal issues:
> a- how to refer to the RDF graph/OWL ontology
> b- how to decide which entailment regime to use
> 
> 
> It would of course be possible to leave both things out of RIF, but I
> think we should at least give people the chance to refer to RDF
> graphs/OWL ontologies.  I also have the feeling that most people in
the
> working group would not have a problem with that.
> First of all, the shape of such a reference would depend our earlier
> decision between directive/syntax extension.
> 
> Then, I see three ways to include such references:
> 1-  use the RIF "imports" statement.  An advantage would be that we
use
> the same key word for all things that are "imported".  A disadvantage
> would be that the term is overloaded.
> 2- define a new keyword, e.g. "data source reference"
> 3- define a range of keywords, one for each entailment regime, e.g.
> "importOWLDL", "importOWLFull"
> 
> If we would go for option 3, we would immediately solve the second
issue
> (b).
> Personally, I don't like option 3, because it always requires to
specify
> the entailment regime.  I would like to make it optional.
> Then, I have a slight preference for option 2, because it matches my
> intuition, but I would not have a problem with option 1.

[PV>] Option 2 also has the advantage of appearing natural to many
potential PRD authors, and by terminology, clarifies the relationship
between rules and data [although I note that for some that will be a
disadvantage].

> concerning issue (b):
> 1- If we want to include references to entailment regimes, we can
> include a keyword "entailmentRegime", and invent IRIs for the
respective
> entailment regimes.
> 2- Another possibility would be to include "switches", i.e., define a
> new keyword for each entailment regime and inclusion of such a keyword
> would mean you want to use it.
> 
> 
> Best, Jos
> 
> 
> [1] http://www.w3.org/2005/rules/wiki/SWC#Annotation_properties
> 
> >
> >
> > I suspect this isn't your style, Jos :-)  -- I don't think it's a
100.0%
> > solution, you have a squint a little --  but it has a certain
elegance
> > which might make it worthwhile.
> >
> > Thoughts?
> >
> > Oh, I should also note that folks have been working on clearing up
OWL
> > Imports with a new spec for OWL 1.1 [3].  I haven't read it yet.  (I
> > doubt it addresses this perspective -- OWL pretends (sometimes
> > awkwardly) to have a subset relationship between dialects, so there
is
> > less need to care about which one you are using.)
> >
> >       -- Sandro
> >
> > [1] big table near the bottom of
> >     http://www.w3.org/2005/rules/wg/wiki/AbstractModel
> > [2] http://www.w3.org/2007/OWL/wiki/XML_Serialization
> > [3] http://www.w3.org/2007/OWL/wiki/Imports
> >
> 
> --
> Jos de Bruijn            debruijn@inf.unibz.it
> +390471016224         http://www.debruijn.net/
> ----------------------------------------------
> Doubt is not a pleasant condition, but
> certainty is absurd.
>    - Voltaire
Received on Thursday, 10 April 2008 16:29:34 GMT

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