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Re: [PRD] a RIF-PRD strawman

From: Paula Patranjan <paula.patranjan@ifi.lmu.de>
Date: Fri, 2 Nov 2007 13:04:26 +0100 (CET)
Message-ID: <49649.>
To: "Christian de Sainte Marie" <csma@ilog.fr>
Cc: "RIF WG" <public-rif-wg@w3.org>

Hi Christian,

since I won't be at the F2F next week, I'm going
to write down a couple of comments I have on your
proposal RIF-PRD.

1. As Harold already mentioned during the telecon
this week, it is not really clear why the notion of
pattern is introduced since they correspond to a
condition in RIF-BLD terms. If I understood it right
you extend RIF-BLD conditions with negative conditions.

I know, you said that the notion of pattern is very
familiar to production rule (PR) system developers, still
I think we shouldn't introduce new notions. My proposal
would be to use conditions instead of patterns and add
a note saying that these correspond to so-called patterns
in some concrete PR languages given as examples.

Also, some researchers make a difference between patterns
and paths for data in specifications of e.g. queries (for
example Xcerpt is a pattern-based query language whereas
XQuery is a path-based query language, both primarily
designed for XML data).

2. When it comes to actions, there is a question stated as
an issue on whether we need update action in RIF-PRD or not.
Do you have here the update statement in mind that signals
that the working memory should be updated now taking into
consideration the given assert, remove, and modify actions?
I noticed that some PR languages support such an explicit
update statement on the working memory (for example the ILOG
Rule Language, IRL, as far as I know), but some do not.

3. As you might know, we had a lecture together with two
colleagues of you from ILOG on reactive rules at the
Reasoning Web 2007 summer school [1]...I learned from this
lecture that PR languages that rely on a data model that is
borrowed from a programming language usually borrow also
some of the language's statements for the action part.
It might be the case that your execute action covers these,
but the question is what happens with the definitions of
e.g. Java methods that are defined outside the rules? Are
they going to be also interchanged? Or ar they going to be
available at some URI?

4. In ILOG JRules you also have the possibility to attach
priorities to rules. Is this going to be covered by an
extended version of the RIF-PRD proposal? Priorities are
also means to implement a conflict resolution strategy;
I know that you discussed also the issue of a resolution
strategy for a set of rules and I think it is kind of
implicit to the rule engine in your case, but priorities
need an explicit specification in the syntax.

5. As a general comment, I think that some of the notions
discussed in the proposal need more explanation. It is
clear that this is just the first version of RIF-PRD, but
for non-experts in the PR field explanation of notions
such as the working memory would be good to have.

6. A couple of nice examples can be found in [1] and they
are given using different PR languages. These examples and
in fact the whole part on PR systems of the paper could be
useful for better understanding the RIF-PRD (as it is at moment
and also in its next versions).

Best regards,

[1] http://www.pms.ifi.lmu.de/publikationen/index.html#PMS-FB-2007-8

> All,
> I just uploaded my (much awaited :-) PRD strawman on the wiki [1] ([2]
> for the more readable TR form).
> It has still no examples in it, nor an XML syntax (that one will be easy
> to derive from BLD's); and, generally, many things are still missing,
> including a section on BLD and PRR compatibility (but I designed it with
> BLD and PRR compatibility in mind, so, that should not be too difficult
> either).
> But I hope that it clear enough to make sense without them (hmmm... Yes,
> I know: I do not have a strong record there... :-)
> [1]http://www.w3.org/2005/rules/wg/wiki/PRdialect
> [2]
> http://burns.w3.org/cgi-bin/wiki_tr?source=http%3A%2F%2Fwww.w3.org%2F2005%2Frules%2Fwg%2Fwiki%2FPRdialect&Go=Go
> Disclaimer: this is *not* ILOG's strawman. It has not been endorsed or
> reviewed in any way by ILOG and it does not represnet ILOG official or
> unofficial view. Of course, it is influenced by ILOG rule language and
> engine, since those are the ones I know best: but I do not even know
> them that good (actually, I certainly know BLD and PRR better than I
> know IRL :-)... I am not even sure that ILOG will like it (I certainly
> hope, and I think, they will, and the other vendors too; but I did not
> check yet). So, again no particular ILOG hat on my head, here. Not sure
> that it is fitting for a chair to submit a strawman, but if it is, I am
> comfortable to submit this with my chair's hat on. If not, consider my
> chair's hat is off (and so I have no hat at all; and now I got a cold...
> c'est malin!).
> Christian
Received on Friday, 2 November 2007 12:04:36 UTC

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