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Re: Comments on * DRAFT * Rules Working Group Charter $Revision: 1.60 $

From: Sandro Hawke <sandro@w3.org>
Date: Tue, 23 Aug 2005 01:39:58 -0400
To: Michael Kifer <kifer@cs.sunysb.edu>
Cc: Jim Hendler <hendler@cs.umd.edu>, public-rule-workshop-discuss@w3.org
Message-Id: <20050823054000.152044EED0@homer.w3.org>


> An exchange language is about XML syntax. You don't need semantics for
> that---only an encoding.

If the XML syntax doesn't have an associated semantics, how can you
tell if you've mapped your language to the standard format correctly?
Not everthing call "implies" means the same thing, right?

> This is not what the proposed draft appears to be
> suggesting.  If an exchange syntax was all that they wanted (and not a
> language for USING rules) then the drafters of that charter are confused,
> IMO.

Rather than saying over and over that I (the charter editor) am
confused, you might try explaining things, preferably using words that
everyone on the list (especially me) can understand.   (But probably
do it bit by bit, in a dialog, rather than writing a mini textbook.)

> I believe that you misunderstood Dieter's comments about OWL. They were
> about the requirements for going forward and why OWL is not the right basis
> for that in certain cases. (Remember the 2 vs. 1 stack debate?)

There are perhaps three separate issues for the draft here:

   1.  Compatibility with OWL.  This seems pretty important to users,
       but presumably could be forsaken for a good enough reason.  I
       took a stab at defining the right kind of compatibility;
       refinements to that definition are welcome.

   2.  Are we aiming for datalog, Horn, FOL, or what?  [Notice I'm
       speaking in generalities here.  We can quibble on whether we
       mean with or without equality, or what kind of negation, or
       even more minute details later.  Broadly, what neighborhood are
       we in?]  It seems like some users want each, and the
       interlingua argument compels us to go with FOL.  Users can just
       use the datalog subset of FOL; they can't just define a
       standard extension of datalog to FOL.

   3.  Is the language monotonic?   Monotonicity appears to be a
       requirement for a Web-based language.  If you want to argue
       about this, let's do it in a thread just about monotonicity. 

> NAF is a special case of SNAF.  Again, the drafters of the charter were
> seriously confused when they said that SNAF is "in" and NAF is "out."

Would you be happy with "NAF" replaced by "unscoped NAF"?  That's all
I meant.  (There's an amusing parallel between this ambiguity in
English and default negation itself.)

> Again, EXCHANGE means XML syntax to me.  Then you need to decide WHAT
> concrete languages you are going to exchange. FOL is NOT a more general
> language -- it is a different language, and it is not a rules language. You
> may need to exchange FOL as well as other rule sets.

Are you thinking an exchange syntax would only let you move rules to
other systems which happened to implement the same type of rules, and
there would be an unlimitted number of vendor-specified types?  That's
kind of what it sounds like you're thinking of, and it's not at all
what we're talking about.  That approach was called "tagging" at the
workshop and in the workshop report (section 3.5).

We're talking about one language which is a superset of many of the
common languages, so it can be used as an interlingua.  You translate
your ruleset into it, and if you can translate it back out into
another vendor's language (because it has enough features), your rules
will mean the same thing.   I'm surprised the mission statement
isn't clear on this.

Perhaps the title should be changed to "Rule Interchange Format (RIF)
Working Group".   The draft does say:

     The Working Group is to specify an interlingua, a common format
     into which existing rule languages can be mapped. This
     interlingua may itself be considered a rule language, and may be
     supported natively by some rule systems in the future, but
     interlingua features are more important than features which make
     the language itself easy to use directly. 

but perhaps that's still not clear enough.

> If we are talking about exchange, then we already have RuleML. It provides
> exchange syntax for a variety of languages. Tweaking it hear and there will
> to the exchange trick.

Can you point us to a specification for RuleML, so vendors and users
can start to see whether it meets their needs?   It seemed pretty
clear that users at the workshop were, in general, not happy with any
of the candidate technologies, but maybe something was missed.

    -- sandro
Received on Tuesday, 23 August 2005 05:40:02 GMT

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