- From: Raphael Volz <rvo@aifb.uni-karlsruhe.de>
- Date: Fri, 4 Jan 2002 20:01:45 +0100
- To: "Mike Dean" <mdean@bbn.com>
- Cc: <www-archive@w3.org>, <www-webont-wg@w3.org>, "Rudi Studer" <rst@aifb.uni-karlsruhe.de>, "Steffen Staab" <sst@aifb.uni-karlsruhe.de>, Jürgen Angele <angele@ontoprise.de>, Alexander Mädche <ama@aifb.uni-karlsruhe.de>, "Frank van Harmelen" <frank.van.harmelen@cs.vu.nl>
- Message-ID: <DMECLAFLIOFJEFFIAJPCIEHKCHAA.rvo@aifb.uni-karlsruhe.de>
------------------------- DAML + OIL Experiences AIFB, FZI @ University of Karlsruhe Ontoprise GmbH ------------------------- This document presents the experiences with DAML+OIL collected in implementing and using several tools (OntoEdit [5], OntoMat [3], KAON Reverse [4]) that can read, write and work with a (large) subset of DAML+OIL. [1] gives an exact survey, which features are supported. Also some relevant experiences from teaching DAML+OIL in several classes given at the University of Karlsruhe are presented. Different representations ========================= Please note that the internal representation of our tools is not based on description logics (being the "standard" mapping from DAML+OIL to logics). OntoEdit relies on F-Logic [5], an object-oriented language and deductive database system. This allows also to have user-supplied rules in ontologies. Mapping DAML+OIL to F-Logic additionally provides a query mechanism, which comes in handy when building applications and tools. KAON Reverse and OntoMat rely on an internal data model whose expressivity essentially corresponds to a relational algebra without negation and complemented with structural recursion. The subset used here essentially corresponds to the intersection of DAML+OIL with RDFS primitives. This representation is also implemented on top of SQl3-compliant relational databases. Consequently, o A web ontology language should be implementable choosing different internal representations and reasoning techniques. o Mappings to rule-based representations simplify the task of constructing a rule / query language for the web ontology language. Multilinguality =============== All our applications and tools support multi-lingual ontologies, however as DAML+OIL does not have a notion of multi-lingual labels and documentation. This feature, which is crucial in an international setting, is a number one requirement for a web ontology. Integration / Interoperability ============================== Our experience from teaching semantic Web issues to students and professionals is that they prefer to think in and exploit the models they have used before, i.e. UML, Java classes, ER models etc. Therefore, we found that many of them have difficulties with the non-frame-like modelling primitives offered by DAML+OIL. The fact, that it is additionally possible to model information that is semantically equivalent using different syntactic encodings (see [6]), leads to difficulties in authoring and additionally hinders understandability. Of course, many applications are existing. We cannot expect everyone to reinvent their stuff, thus a web ontology language should leverage primitives to which systems can map their own (alien) conceptual models easily. Thus a smooth integration with the existing modelling world should be one of our principle goals. Modularization ============== As of now, our tools don't support modularization of ontologies yet. We are currently working on modularization support but will not restrict ourself on the intended semantics of daml:imports, which only allows to (transitively) import all definitions contained in a different file. To make it short, we plan to allow: o all statements in a file (~ daml:imports) o a collection of definitions (using a home-made collection primitive) o single definitions o single definitions together with conceptually related definitions Documentation ============= The possibilities given in DAML+OIL to document an ontology is restricted to version information and comments. This is not sufficient. We use the full set of elements defined by DC within our own tools. Eventually it should also be possible to attach several documentation parts to an ontology (collections of statements) within one file. Within the OntoWeb portal application DC markup given for a set of RDFS statements is used to provide authorship information when content is syndicated from different community members. Meta-Model ========== The primitives offered by a web ontology language should be easily extendable. For example KAON Reverse and Ont-O-Mat would benefit of new property type "KeyProperty", which asserts that there cannot be two distinct instances x1, x2 which have the same range for a property. This requires an extensible meta-model for the web ontology language N-ary Relations =============== Neither RDFS nor DAML+OIL allows for n-ary relations at the moment although modelling is much more natural having a primitive for n-ary relations instead of decomposition into sets of binary relations as it is proposed now. In many application scenarios this kind of information must be modelled. Usage Perspectives ================== Up till now design choices taken for DAML+OIL were mainly choosen for a specific user group: ontology modellers. It seems to us that few conciderations have been made for two other import user groups: the people that actually build tools to support the language and those people that actually provide the good-old A-Box: Instance data that provides the flesh in the Semantic Web. As our experience from actually implementing and using applications show, other aspects of a language become relevant, we could have been aware of earlier. Extensability ============= While rules and query languages are a non-issue of our group. The current working group aim, working with DAML+OIL, is not practical without them. One of our main reasons for not working directly with DAML+OIL, but with mappings into other paradigms were the lack of rules and especially the query language. In order to be able to provide a query language and a rule language reasonably soon after the definition of the ontology language, we propose that the theory for querying and rules based on the ontology language should mostly be understood during the design process. Otherwise, the time lag between theoretical development and practical usability may endanger the success of the ontology language. Therefore, we'd actually prefer a simpler language than DAML+OIL that uses layers of language features to allow early adaption of core features ! (! certainly something with a formal semantics !) References: ----------- [1] http://lists.w3.org/Archives/Public/www-rdf-logic/2001Dec/0018.html [2] http://citeseer.nj.nec.com/kifer90logical.html [3] http://ontobroker.semanticweb.org/annotation/ontomat/ [4] http://kaon.semanticweb.org/kaon/REVERSE [5] http://ontoserver.aifb.uni-karlsruhe.de/ontoedit/ [6] http://www.semanticweb.org/SWWS/program/full/paper40.pdf -- Raphael Volz Tel: 49 721 608-7363 Institut AIFB Web: http://www.aifb.uni-karlsruhe.de/WBS/rvo Uni Karlsruhe (TH) EMail: volz@aifb.uni-karlsruhe.de PGP-Key Fingerprint: C5A1 52FA D0F1 47B9 7075 1F22 F3E3 BEE2 68BB 1643
Received on Friday, 4 January 2002 14:03:06 UTC