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blog名称:彼岸·花
日志总数:39
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建立时间:2005年8月6日




[一路前行]A discussion about Jess and Racer
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子轩 发表于 2006/12/4 8:37:41

Gerhard AustallerFri, 27 Oct 2006 14:39:25 -0700 Hi I somehow completely lose overview on "semantic" technologies... Does anybody know or is willing to explain where the difference/overlap... between "expert systems" like JESS/CLIPS and ontologies (with reasoners) is. Because of the rules it appears that expert systems are more powerful but maybe there is something I can express with ontologies that I can not within expert systems. Another question is about RACER PRO. The query language NRQL looks like a rule language in JESS. Is it RACER PRO's NRQL as powerful as the rules in JESS? Maybe anybody knows both systems and could give a hint or a link. And last, does anybody know a way to import a OWL ontology into JESS. Most solutions I know lose almost all restrictions. Is this an implementation issue or is it because JESS (experts system in general) are not to be used with "ontologies". Thank you very much! Gerhard Martijn TrommFri, 27 Oct 2006 16:17:47 -0700Hi Gerhard, I'm not very experienced with the technical of side of this, but I know something about rules and ontologies. Rules can only work on some datamodel. An ontology is nothing more than a formalized conceptualisation, so a extended datamodel. Extended with what? Wel with, constraints, typing, hierarchies, and rules. Expert systems can be seen as one of more possible implementations of logic within applications. And when that logic is highly irregular and prone to change than it is a good choice. OWL is one of more possible notations of ontologies. w3c is busy with standards for OWL rules (very similar to RuleML I believe). So rules and ontologies are a perfect couple. Expert systems shells are terrific middle ware for dealing with the rules that will be formulated upon ontologies. One of the big issues in this discussion is whether Owl applications should be Closed World applications. (OWL is not closed by default, but one can state a lot more rules under the CWA) cheers, Martijn Samson TuMon, 30 Oct 2006 14:49:41 -0800The contrast is between description-logic (DL) reasoning (of which OWL is a variety) versus rule-based reasoning. Description-logic reasoning gives you runtime class-subsumption checking and classification of individuals based on necessary and sufficient definitions of classes. Rule-based reasoning is not designed to do these tasks. On the other hand, DL reasoning can't handle rules like (Father ?x ?y)(Brother ?x ?z) => (Uncle ?z ?y). OWL has been augmented with a rule-language called SWRL. DL reasoning typically makes open-world assumption. Jess uses closed-world assumption. Making sense of DL restrictions (e.g., class expressions) typically requires the use of DL reasoner, which is difficult to simulate using something like Jess. Ontologies can be defined using DL language like OWL or frame-based language (e.g., Protege frame). Protege frame also makes closed-world assumption. Thus, JessTab works well integrating frame-based Protege ontologies with Jess. Samson Gerhard AustallerTue, 31 Oct 2006 04:26:17 -0800Hi > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of Samson Tu > Sent: Monday, October 30, 2006 11:20 PM > To: jess-users@sandia.gov > Subject: Re: JESS: JESS vs RACER > > > The contrast is between description-logic (DL) reasoning (of which OWL > is a variety) versus rule-based reasoning. Description-logic reasoning > gives you runtime class-subsumption checking and classification of > individuals based on necessary and sufficient definitions of classes. > Rule-based reasoning is not designed to do these tasks. On the other > hand, DL reasoning can't handle rules like (Father ?x ?y)(Brother ?x ?z) > => (Uncle ?z ?y). > > OWL has been augmented with a rule-language called SWRL. > > DL reasoning typically makes open-world assumption. Jess uses > closed-world assumption. Thx for answer. OK. Now we are getting to the point. What I really want to understand is where the difference is between rule "extensions" to ontologies and rules from expert systems. What I'd like to is create new individuals ("add a fact") in my ontology by using a rule language (like SWRL). Of course this new individual my trigger other rules and so on until a stable state. I'd like to program declarative as I am used to with e.g. JESS. > Making sense of DL restrictions (e.g., class expressions) typically > requires the use of DL reasoner, which is difficult to simulate using > something like Jess. But in principle there is no obstacle to merge the power of ontologies (based on DL) and expert systems? > Ontologies can be defined using DL language like OWL or frame-based > language (e.g., Protege frame). Protege frame also makes closed-world > assumption. Thus, JessTab works well integrating frame-based Protege > ontologies with Jess. But the documentation of JessTab says that one OWL constraints and expressions are not supported. So restrictions are not lost? Gerhard Samson TuTue, 31 Oct 2006 10:07:28 -0800 Gerhard Austaller wrote: .. Thx for answer. OK. Now we are getting to the point. What I really want to understand is where the difference is between rule "extensions" to ontologies and rules from expert systems. What I'd like to is create new individuals ("add a fact") in my ontology by using a rule language (like SWRL). Of course this new individual my trigger other rules and so on until a stable state. I'd like to program declarative as I am used to with e.g. JESS. I am not sure I can add more than what I said already. With rule extensions to DL languages, the rule system has to take into account the semantics of DL descriptions. To create new instances in SWRL, I think you need to have a "built-in" that does it. Creating new instances is not part of the language. Making sense of DL restrictions (e.g., class expressions) typically requires the use of DL reasoner, which is difficult to simulate using something like Jess. But in principle there is no obstacle to merge the power of ontologies (based on DL) and expert systems? No, that's what SWRL and other semantic web rule languages are about. Ontologies can be defined using DL language like OWL or frame-based language (e.g., Protege frame). Protege frame also makes closed-world assumption. Thus, JessTab works well integrating frame-based Protege ontologies with Jess. But the documentation of JessTab says that one OWL constraints and expressions are not supported. So restrictions are not lost? Not sure what you mean. With OWL, JessTab doesn't Samson TuTue, 31 Oct 2006 10:07:28 -0800 Gerhard Austaller wrote: .. Thx for answer. OK. Now we are getting to the point. What I really want to understand is where the difference is between rule "extensions" to ontologies and rules from expert systems. What I'd like to is create new individuals ("add a fact") in my ontology by using a rule language (like SWRL). Of course this new individual my trigger other rules and so on until a stable state. I'd like to program declarative as I am used to with e.g. JESS. I am not sure I can add more than what I said already. With rule extensions to DL languages, the rule system has to take into account the semantics of DL descriptions. To create new instances in SWRL, I think you need to have a "built-in" that does it. Creating new instances is not part of the language. Making sense of DL restrictions (e.g., class expressions) typically requires the use of DL reasoner, which is difficult to simulate using something like Jess. But in principle there is no obstacle to merge the power of ontologies (based on DL) and expert systems? No, that's what SWRL and other semantic web rule languages are about. Ontologies can be defined using DL language like OWL or frame-based language (e.g., Protege frame). Protege frame also makes closed-world assumption. Thus, JessTab works well integrating frame-based Protege ontologies with Jess. But the documentation of JessTab says that one OWL constraints and expressions are not supported. So restrictions are not lost? Not sure what you mean. With OWL, JessTab doesn't take into account OWL constrains and expressions, but nothing is "losttake into account OWL constrains and expressions, but nothing is "lost……见http://www.mail-archive.com/jess-users@sandia.gov/msg08868.html


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