From: pat hayes (phayes@ai.uwf.edu)
Date: 02/25/03
Attached are some @comments@ on Gerd's statement. ---- Statement by Gerd Wagner prepared on request of the Joint Committee . 13-Feb-2003 It is hard to define what is a rule and, although we can come up with a formal account for a specific type of rule, I think we should better not try to find a definitive formal account for "rules", in general. @ Unless we do, it seems to me that the discussion is vacuous. We literally do not know what we are talking about. @ Rather, I suggest to consider rules at three different levels [ 1]: At the problem domain level, rules are statements that express (certain parts of) a business/domain policy (e.g., defining terms of the domain language, defining or constraining domain operations) in a declarative @ Please say what is meant by 'declarative' here. See later comments. @ manner, typically using natural language or a visual language. Some examples: "A gold customer is a customer with more than $1MM on deposit." "The driver of a rental car must be at least 25 years old." @ That is not a declarative statement, at least with its usual intended meaning in such a context, i.e. to constrain behaviors. @ "If any 3 of the named analysts report a strong buy on the same stock within the same day and before the market closes, then buy 1000 units of that stock." @ That is also not a declarative: it is an imperative. @ At the (platform-independent) computational level, rules are formal statements that operationalize domain policies and can be easily mapped into executable statements of a programming platform. @ That seems to cover any programming platform at all. @ Rule languages used at this level are RuleML 0.82, SQL-99, OCL 2.0, ISO Prolog or KIF. @ KIF is purely an assertional logic, and cannot be 'easily mapped' into executable statements. In fact I don't think it can be mapped into any kind of executable statements in any reasonable sense of 'mapped'. @ At the (platform-specific) execution level, rules are statements in a specific executable language, such as Jess, XSB or the Microsoft Outlook Rule Wizzard. In any case, rules are modular, stand-alone units, which directly support or involve some form of reasoning. @ To me, what you have said is that rules are chalk, and therefore rules are cheese. Look, both the second and third items in your list emphasize *executable*; you are apparently talking about code, not assertions. But then you immediately go on to sum this up using the words 'stand-alone' and 'reasoning'. Reasoning and computation are NOT the same; they are fundamentally different. So which one are we talking about here? @ They may, for instance, specify derivations (e.g. for defining derived concepts), static and dynamic integrity constraints (e.g. for constraining the state space or the execution histories of a system/agent), reactions (e.g. for specifying the reactive behavior of a system/agent in response to events) @ in what sense is a 'reaction' anything to do with reasoning?? @ Given the linguistic richness and the dynamics of natural problem domains, it should be clear that any specific account of rules, such as classical logic Horn clauses, must be viewed as a limited descriptive theory that captures only a certain fragment of the entire conceptual space of rules @ My point has always been that this is meaningless, or empty, since there IS no conceptual space of 'rules' (other than the whole of computation: and in your case, even more, including all of human behavior). You havn't said anything to make me think I am wrong. @ , and not as a definitive, normative account (see also the discussion at http://lists.w3.org/Archives/Public/www-rdf-rules/2001Sep/0079.html ). We need a pluralistic approach to the heterogeneous conceptual space of rules. Therefore, in RuleML a family of rule languages capturing the most important types of rules is going to be defined. Each of these languages will have a recommended formal semantics, but may have one or more alternate acceptable semantics. This will accommodate various formalisms based on non-standard logics, supporting temporal, fuzzy, defeasible and other forms of reasoning. @ It would be more helpful if you could say what they might NOT include. @ Pat Hayes -- --------------------------------------------------------------------- IHMC (850)434 8903 or (650)494 3973 home 40 South Alcaniz St. (850)202 4416 office Pensacola (850)202 4440 fax FL 32501 (850)291 0667 cell phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes s.pam@ai.uwf.edu for spam
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