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Re: Reference vs import <-- RIF Core shortened

From: Chris Welty <cawelty@gmail.com>
Date: Mon, 24 Nov 2008 10:15:05 -0500
Message-ID: <492AC4F9.9090906@gmail.com>
To: Patrick Albert <palbert@ilog.fr>
CC: RIF WG <public-rif-wg@w3.org>

Patrick Albert wrote:
> I do support :)!

What is it you support?  A restricted notion in CORE of the BLD member and subclass?

> I believe that PRD needs to support an object model such as the one
> found in the UML class diagram. It is very simple and obvious --
> classes, subclasses, attributes and links with cardinality
> specifications -- every software developer knows it or at least has been
> exposed to it, it is supported by many tools, and every Business Rules
> system supports it.

Certainly the notion of member and subclass in BLD is not the same as the one in 
UML, so if this is the objective BLD and PRD have a different notion of class 
and subclass.

> The problem I see though to have it in CORE, is the set-based
> interpretation of the inter-objects links, when the BLD frames have a
> one-tuple-at-a-time interpretation. 

I have no idea what you mean by this, but perhaps it doesn't matter.  It seems 
to me the point is that they are *different*, in which case they don't belong in 

I am not intending to express an opinion here, just trying to congeal the 
threads.  We have a resolution in the group about "no hidden features" which I 
intend to uphold - that is that no part of the syntax will be reused *to mean 
something different*.

So, it seems to me that while the similarities between what I'll call 
prd:subclass/prd:member and bld:subclass/bld:member are intruiging, there are 
differences - they are not the same thing so there is no "CORE" notion.


>  Patrick. 
> -----Original Message-----
> From: public-rif-wg-request@w3.org [mailto:public-rif-wg-request@w3.org]
> On Behalf Of Chris Welty
> Sent: dimanche 23 novembre 2008 03:07
> To: RIF WG
> Subject: Re: Reference vs import <-- RIF Core shortened
> 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?
> -Chris
> 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 Monday, 24 November 2008 15:15:47 UTC

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