- From: Hassan Aït-Kaci <hak@ilog.com>
- Date: Thu, 04 May 2006 09:50:35 -0700
- To: "Peter F. Patel-Schneider" <pfps@inf.unibz.it>
- CC: public-rif-wg@w3.org
Hello, This is in response to PFPS's mail (http://lists.w3.org/Archives/Public/public-rif-wg/2006May/0056.html) that was itself commenting on my own mail (http://lists.w3.org/Archives/Public/public-rif-wg/2006May/0052.html) that was itself commenting on the proposal draft by Boley et al. (http://lists.w3.org/Archives/Public/public-rif-wg/2006Apr/0068.html). There are general and specific points in response to Peter's comments. First, the general points. 1. I am not embracing all the details of the said proposal, and some objections may be related to some that your voiced yourself, I think (see below). The point, it seems, is to discuss what we agree and disagree on in order to find a workable consensus. In other words, let us bbe constructive. 2. I "admire" more the fact that Boley et al.'s are proposing a concrete and constructive first step towards specifying a working Rule Interchange Format - one in fact, that makes sense to me as workable, and could be developed into a clear specification of what such a RIF may look like and how it may be used to achieve interchange of rule-based programs. Now the detailed points (quoting from your message): PFPS > ......................................................................... PFPS > PFPS > This is a view of the RIF starting from the parts of the proposal by Boley PFPS > et al that Ait-Kaci likes. Optional or questionable parts are in []s. PFPS > PFPS > PFPS > The RIF is a language for interchanging rules. PFPS > PFPS > ABSTRACT SYNTAX PFPS > PFPS > The basic syntactic categories in the RIF and their construction are: PFPS > PFPS > 1/ Atomic constructs PFPS > - an infinite supply of constants PFPS > - a set of data values - both typed and untyped PFPS > - an infinite supply of variables PFPS > - an infinite supply of n-ary functions for each n>=1 PFPS > [should functions be typed?] PFPS > - an infinite supply of n-ary predicates for each n>=1 PFPS > [should predicates be typed?] PFPS > PFPS > Constants, functions, and predicates are IRIs. PFPS > Typed and untyped data values are constructed according to the abstract PFPS > principles underlying data values in RDF. PFPS > That could indeed be a start. The RIF-RAF also distinguishes non-interpreted functions (constructors) and interpreted functions. Regarding types (or sorts), again, the RIF-RAF accommodates such notation. Many (if not most?) systems are typed (JRules, LIFE, Mercury, Flora-2) Systems. Frame-like notation for classes and objects (as used in JRules, LIFE, Flora-2) is also a notation that needs to be representable. The draft proposal is just a ... draft. It needs elaboration of course. I think Michael's message (http://lists.w3.org/Archives/Public/public-rif-wg/2006May/0061.html) makes this point clearly. PFPS > 2/ Terms - a well-founded syntactic category constructed from PFPS > - constants PFPS > - variables PFPS > - data values PFPS > - function applications - an n-ary function with an n-tuple of terms There could be also other notations extending the basic terms - namely so-called "Frame-like" terms (e.g., psi-terms, F-Logic terms, etc., ....). PFPS > PFPS > 3/ Formulae - a well-founded syntactic category constructed from PFPS > - predicate applications - an n-ary predicate with an n-tuple of terms PFPS > - & of a sequence of formulae PFPS > - | of a sequence of formulae PFPS > - N of a formula PFPS > - n of a formula PFPS > - A of a variable and a formula PFPS > - E of a variable and a formula PFPS > - = of an ordered pair of formulae PFPS > [There may be a few more formulae constructors.] For example, constraints. PFPS > PFPS > 4/ Rules - a well-founded syntactic category constructed from PFPS > - deductive rule of an ordered pair of formulae PFPS > - normative rule of a formula PFPS > [There may be a few more rule constructors.] PFPS > PFPS > [There may be a few more syntactic categories to support other kinds of PFPS > rules.] Indeed, such as - why not? - Rewrite Rules (e.g., Maude, OBJ, ELAN) , or Constraint-Handling Rules (CHR), for example. PFPS > INTERCHANGE SYNTAX PFPS > PFPS > There will be an XML dialect that provides an interchange syntax for the PFPS > above abstract syntax. An XML Schema will govern this dialect. Correct. PFPS > EXTENSIBILITY PFPS > PFPS > Subsets of the above syntax that are of current commercial or technical PFPS > interest will be identified. Yes. And a framework will be supported to map new rule-based languages in the RIF conceptual ontologies (along syntax, semantics (yes!), and pragmatics). PFPS > SEMANTICS PFPS > PFPS > None. Notwithstanding Michael's answer to the above (see http://lists.w3.org/Archives/Public/public-rif-wg/2006May/0061.html) I am as well most puzzled with your perception. In fact, since the beginning, the questions of "Is the RIF a language?" and if so, "What is its syntax and its semantics?", have not been clearly settled. In my understanding, the RIF is not a language but a notational protocol using accepted W3C standards (XML, RDF, OWL, ...) for representing families of rule-based languages (as more or less circumscribed by the RIF Charter). Its objective is to enable interchange of programs expressed in various existing rule-based idioms to be shared or borrowed among various rule-based systems. Program constructs expressed in various idioms that are compliant with the RIF should be mappable to concepts and features of the ontology of the RIF conceptual lattice (rule language classification). Regarding semantics? Again, the RIF IS NOT A LANGUAGE, but a notation for (families of rule) languages. The rule languages that are representable using this notation have themselves a semantics, of course (presumably based on the syntax they understand - see Frank MacCabe's message http://lists.w3.org/Archives/Public/public-rif-wg/2006May/0063.html. So what is the semantics of a RIF notation? It is in fact a representational semantics: the XML elements expressing RIF constructs denote abstract representation of meta-linguistic objects that are interpretable by client systems (compilers or interpretors) based on the syntactic, semantic, and pragmatgic features that the RIF annotation provides. PFPS > Q1 (to everyone): Is this what you want out of the RIF? I want what I described - I want the RIF to enable effective rule interchange. PFPS > Q2 (to Hassan): Is this what you like in the Boley et al proposal? Yes. PFPS > Peter F. Patel-Schneider -hak -- Hassan Aït-Kaci ILOG, Inc. - Product Division R&D tel/fax: +1 (604) 930-5603 - email: hak @ ilog . com
Received on Thursday, 4 May 2006 16:49:04 UTC