- From: <Joachim.Peer@unisg.ch>
- Date: Sat, 20 Sep 2003 17:30:46 +0200
- To: www-ws@w3.org
hi all, i was wondering what can be considered the "semantic essence" of DAML-S, and i was also wondering whether DAML-S/Semantic Web Service Description could be decoupled a bit from DAML+OIL. 1. my problem Currently, DAML-S is consequently tied to DAML+OIL (or OWL), which in my opinion, is not always optimal: * No "native" language support to represent vital parts of a service's semantics: in DAML+OIL, there is no language level construct to represent logical variables, hence helper constructs such as "profile:parameterName" must be used. Further, it is impossible to freely represent relations/functions between input and outputs, preconditions and effects, whereas in a simple rule based format i could write something like Person(X), Output= phoneNumber(X). * Usability issues (personal taste): DAML+OIL is tied to to RDF serialization. This concrete representation (usally RDF/XML) leads to relatively large files that are hard to understand and maintain, at least if plain text editors are used [1]. This clearly heightens the entry barrier for web service developers. So, we have the following situation: a) surely everything can be represented somehow by DL ontologies, and DAML-S does just that. b) but on the other hand, not all problems can be successfully solved by DL based reasoning only. I think it is safe to say that Description Logic (DL) based reasoning is a useful but not sufficient technique for applications like automatic Web Service retrieval and composition. While there exists much work on using pure DL reasoning for Web Service retrieval (e.g. [2]), lot's of other work, especially in the context of Web Service composition relies on non-DL based techniques, e.g. AI planners [3]. To me, this is a paradox situation. What is the technical justification for using DAML throughout the whole DAML-S concept even where disadvantages outweight the benefits? I.e. why do i deal with the cumbersome aspects of DAML+OIL when DAML+OIL reasoning will not solve my problems? Why can't DL's use be restricted to those parts of a service representation where it clearly pays off, e.g. representation of input and output types, or qualitiative service properties? 2. a potential solution I think this issue can be addressed by de-coupling the semantic aspects of DAML-S from its notational aspects. I am not sure if this has been proposed before, because it is such a simple idea, but i would really like to see something like a "kernel" which tells us how a web service should be described. This kernel would capture just the _essence_ of what can be considered the core of the current DAML-S concepts, e.g. the IOPE semantics, the semantics of the process composition constructs and so forth. Fortunately, much work has been done to carry that out (e.g. [4] or the recent posting by McDermott [5]) In addition to this kernel, mappings could be created to several different styles of notations, such as "classical" DAML-S and various alternative or leightweight dialects, which can be transformed into each other. The abstract semantic core should be designed with the issues related to computational complexity in mind, and it should also make use of core Semantic Web techniques (e.g. the use of ontologies to represent type information) Abstract/Conceptional Semantic Web Service description concept (ie. DAML-S' core or "semantic essence") | _______________|________________ | | | transform. transformation transformation rules rules rules | | | | | | DAML+OIL encoding X encoding Y endoding (e.g. using (e.g. using Rules in prolog RuleML/XML) style) The benefit of such a decoupled hierarchy of languages would be: 1) the semantics of DAML-S could be expressed in very straightforward, more transparent and still formal/obliging way. 2) people could chose from a variety of representational styles, without necessarily sacrificing interoperability. Specialized formats could be created to satisfy requirements from various communities (e.g. the WSDL community) what do you think about this? which document would you recommend as (a starter for) the DAML-S core/essence document ? kind regards, Joachim [1] Marta Sabou, Debbie Richards, and Sander van Splunter: An experience report on using DAML-S. In The Proceedings of the Twelfth International World Wide Web Conference Workshop on E-Services and the Semantic Web (ESSW '03). Budapest, 2003 [http://www.iids.org/publications/essw03.pdf] [2] Lei Li and Ian Horrocks. A software framework for matchmaking based on semantic web technology. In Proc. of the Twelfth International World Wide Web Conference (WWW 2003), pages 331-339, 2003. http://www.cs.man.ac.uk/~horrocks/Publications/download/2003/p815-li.pdf [3] Dan Wu, Bijan Parsia, Evren Sirin, James Hendler and Dana Nau: Automating DAML-S Web Services Composition Using SHOP2. ISWC-2003 [4] Concurrent Execution Semantics for DAML-S with Subtypes, Anupriya Ankolekar, Frank Huch, Katia Sycara, The First International Semantic Web Conference (ISWC), Sardinia (Italy), June, 2002. http://www.daml.org/services/ISWC2002-ExSem.pdf [5] McDermott D., posting "DAML-S formal semantics"http://lists.w3.org/Archives/Public/www-ws/2003Sep/0016.html Joachim Peer Research Assistant MCM Institute, University of St. Gallen Blumenbergplatz 9, 9000 St. Gallen, Switzerland Phone: ++41 (0) 71 224 3441, Fax: ++41 (0) 71 224 2771
Received on Saturday, 20 September 2003 11:31:02 UTC