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Re: Reference vs import <-- RIF Core shortened

From: Chris Welty <cawelty@gmail.com>
Date: Sat, 22 Nov 2008 21:06:58 -0500
Message-ID: <4928BAC2.2080507@gmail.com>
To: RIF WG <public-rif-wg@w3.org>

I certainly see the intuition for member and subclass in Core, but it appears 
its support has diminished to a) only Gary and b) only for a restricted version 
of them.

Is this accurate?


Gary Hallmark wrote:
> challenge accepted, so below
> Christian de Sainte Marie wrote:
>> Dave,
>> thanx for the clarification.
>> Here is how I understand PRD needs, at this point. Please, all, 
>> complete and/or correct me:
>> 1. Production rules needs subclass relationships. But in most, if not 
>> all, cases, the class hierachy is fixed and there is, therefore, no 
>> need to test it explicitely. However, it may be used by classification 
>> tests, and it is, thus, needed in the semantics. Since it is, in most, 
>> if not all, cases, externally defined, it has to be imported. But the 
>> import can be specified without requiring that subclass relationships 
>> be explicitely asserted in rules or facts.
>> Hence, (my current understanding is that) PRD can do without ## in the 
>> concrete syntax.
> very odd to have ## in the abstract syntax and semantics but not let 
> people use it.
>> So, it would be interesting to challenge that assertion:
>> 1a. What would be an use case where a subclass relationship test would 
>> need be explicit in the condition of a rule (as opposed to the test 
>> being carried silently as a consequence of importing the class 
>> hierarchy)?
> Here's a production rule I'd very much like to write if I'm trying to 
> translate between RDF and Java objects:
> if ?o # ?c1 and ?o # ?c2 and not(?c1 = ?c2 or exists( ?c ?o # ?c and ?c 
> ## ?c1 and ?c ## ?c2))
> then ConstraintViolation("found an object that cannot have a Java Object 
> Model")
>> 1b. What would be an use case where a subclass relationship would need 
>> be explicitely asserted in a fact (as opposed to being taken into 
>> account as a consequence of importing the class hierachy)?
> Let's say several vendors have RIF translators but not all have an 
> import mechanism that works for Java objects, XML documents, and OWL 
> ontologies.  An enterprising vendor could build a comprehensive set of 
> importers that output standard RIF so it can be used with all the 
> current and future RIF translators (assuming the RIF dialect supports # 
> and ## facts, of course)
>> 1c. What would be an use case where a subclass relationship would need 
>> be asserted as a consequence of a rule (as opposed to the class 
>> hierachy being immutable)?
> I don't want to support this
>> 2. Production rules need to test membership relationships, though. But 
>> in most, if not all, cases, class membership is immutable. So that 
>> class membership needs be asserted only at an object's creation. It 
>> can thus be part of the semantics of the creation action (e.g. as 
>> proposed in [1]).
>> Hence, (my current understand is that) PRD can do with # being allowed 
>> in tests and variable bindings only.
> No, we need # and ## as facts to support the Import Vendor use case.
>> The only challenge to that assertion that I can imagine would be an 
>> use case for class membership assignement or mutation as a consequence 
>> of a rule (but you all know how poor my imagination :-)
> I don't want to support # and ## as conditional assertions, only as 
> facts (i.e. unconditional)
>> 2a. What would such an use case look like?
>> 2b. Other ways to challenge the assertion, anyone?
>> Dave Reynolds wrote:
>>> The proposal we discussed some weeks ago (but seem never to have 
>>> formally adopted) was to only have # and only in rule conditions. 
>>> That is appealing to be me because then I don't have to implement 
>>> anything (if you can't assert data you can't test it!).
>> The semantics of PRD is specified with respect to a data source. But, 
>> as far as I understand, it does not require the data to be explicitely 
>> asserted as facts (as opposed to being imported by reference to the 
>> data source). So that, as soon as we will have specified that import, 
>> it will be possible, in PRD at least, to have facts to test class 
>> membership, whether PRD allows to assert facts or not...
>> Cheers,
>> [1] http://www.w3.org/2005/rules/wiki/Alt_AbstrAction
>> Christian

Dr. Christopher A. Welty                    IBM Watson Research Center
+1.914.784.7055                             19 Skyline Dr.
cawelty@gmail.com                           Hawthorne, NY 10532
Received on Sunday, 23 November 2008 02:07:41 UTC

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