Re: can we all work together?

With regards to Gary's useful comment, I would like to stress again that 
phase 1 is _not_ about interchanging Horn rules: phase 1 is about 
building the foundation of RIF.

The WG "mission in the first phase is to produce a W3C recommandation 
for a very simple and yet useful and extensible format". Phase 1 must 
design the foundation for a RIF that can be extended to cover the 
relevant rule languages and usage scenarios while ensuring compatibility 
with other relevant standard (including RDF and OWL; PRR; etc).

As the specification of such foundations would not necessarily enable, 
per se, the interchange of one single rule, the charter mandates us to 
support at least the interchange of Horn-like rules. This is to make 
sure that phase 1 RIF is useful to interchange at least some kind of 
rules, without forcing us to deal with the complex and potentially 
contentious problem of multiple semantics (some, horresco referens, 
being even possibly operational :-)

My point is that at least Horn does not mean only Horn: nothing should 
stop us from harvesting any useful low hanging fruit we can find, 
provided that we specify the extensibility and compliance models, XML 
syntax, the basics of datatype support and data source access etc; and 
the semantics for Horn rules, of course.

In summary, Garys' proposal can be extended without charter's violation to:
1. start with a common (XML) syntax and model theory for conditions 
(actually: logical sentences), extending Boley et al proposal to include 
any useful low hanging fruit (slotted atoms, types etc come to mind), 
without specific consideration for Horn restrictions. But including 
everything mandated in the charter, of course, like how it interacts 
with OWL etc.;
2. add the specification for the head of Horn rules (probably as a 
restriction on the step 1 language) and the semantics for Horn rules 
(seen like that, that step looks like a no-brainer; but I may be wrong);
3. add the specification for the conclusion of other kind of rules, with 
the appropriate semantics (for the rules), including PR actions (and 
semantics).

The extensibility model that will allow it is phase 1, but how we 
specify the appropriate semantics for different kinds of rules in as 
uniform a way as possible is typically a question for phase 2 (Hassan's 
proposal to use rules, à la Natural Semantics, is one possible approach; 
there are certainly others).

Notice that specifying a step 1 language that covers the core 
requirements of many different rule languages (including PR ones) would 
be a real benefit in itself, even though step 3 will probably not be 
standardised before phase 2. It would, in particular, enable advance 
implementations beyond Horn rules, thus initiating deployement, on the 
one hand; and suscitating useful proposals and raising concrete issues 
to be considered in phase 2, on the other hand.

Christian

Received on Thursday, 1 June 2006 13:26:53 UTC