1. Evgeny Zolin, School of Computer Science, University of Manchester, UK, ezolin@cs.man.ak.uk Andrey Bovykin, Department of Computer Science, University of Liverpool, UK, andrey@csc.liv.ac.uk We present a formalism for describing Semantic Web Services Main features of the approach: It deals with information providing ( stateless ) services Enables for service discovery of high precision / recall Service descriptions use terms from background ontology The problem of matching web services is decidable Compatible with standard approaches (OWL-S, WSMO) Describing Services Inputs Outputs x1x1 x2x2 xmxm y1y1 ynyn z1z1 z2z2 zrzr A Service Description consists of: specification of inputs x i and their types X i (the information accepted by a service) specification of outputs y j and their types Y j (the information returned by a service) specification of relationships between the inputs and outputs (which has the form of a conjunctive query, see [2] for details) specification of relationships between the inputs and outputs (which has the form of a conjunctive query, see [2] for details) Example of a service description A service advertisement S: a service returns the list of wines that are produced in a specified geographical region: Note: terms “ GeoRegion ”, “ LocatedIn ” etc. come from a geo-ontology; “ Wine ”, “ Produces ” etc. from a wine ontology Input: g: GeoRegion Output: w: Wine Relationship: THERE IS SOME f: f: WineGrower & f LocatedIn g & f Produces w Input: g: GeoRegion Output: w: Wine Relationship: THERE IS SOME f: f: WineGrower & f LocatedIn g & f Produces w REFERENCES: [1] D.Martin et al. Bringing Semantics to Web Services: The OWL-S Approach. In Proc. of SWSWPC’04. 2004 [2] Duncan Hull, Evgeny Zolin, Andrey Bovykin, Ian Horrocks, Ulrike Sattler, Robert Stevens. Deciding Semantic Matching of Stateless Services. In Proc. of AAAI’06, Boston,USA, July 16-20, 2006 [3] D.Hull, K.Wolstencroft, R.Stevens, C.Goble, M.Pocock, P.Li, T.Oinn. Taverna: A tool for building and running workflows of services. In Nucleic Acids Research, 34:W729-W732 (Web Server Issue), 2006 Acknowledgements and links: The work is supported by EPSRC, grants GR/S63168/01, GR/R67743/01 DynamO: http://dynamo.man.ac.uk my Grid: http://www.mygrid.org.uk Service Matching Abstract A service advert S matches a service request Q, where: S has input type X, output type Y, relationship F ( x, y ) Q has input type Z, output type W, relationship G ( x, y ) w.r.t. a background ontology T if two conditions hold: Applicability: Z is a subtype of X w.r.t. T ( Z X ) Coherence: the services S and Q always 1 return the same answers on any input a from Z : for any individual b, the conditions W ( b ) and G ( a, b ) hold iff Y ( b ) and F ( a, b ) hold. _____________________ 1 For any data (i.e., an ABox) that conforms the scheme T. See [2] for detailed definition. Comparison to related approaches In the presented approach, service matching problem is decidable. But only info-providing services are covered. In OWL-S [1], a Service Profile describes IOPE (inputs, outputs, preconditions, and effects), thus stateful services are covered. But for stateless services, it has no way of relating inputs and outputs, due to limitations in the OWL. The Web Services Modelling Ontology (WSMO) has a mechanism for relating inputs to outputs, but the resulting matching condition is not decidable, due to unrestricted use of the First-Order Logic (FOL). Conclusions and future work The approach is applicable to semantic matching of web services in bioinformatics, where about 3000 heterogenious services are used by scientists [3]. We are currently implementing this matchmaking algorithm in a public registry of biomedical services. In future, we plan to investigate applicability of the approach to semantic description and retrieving of workflows (i.e., compositions of web services). Workflows are commonly used by scientists conducting experiments on genomic data. Examples of services and matches A service request Q 1 : a user is looking for a service that returns the list of wines that are sold in a specified region: Note: the services S and Q 1 have the same inputs/outputs, but they perform different functions, so they do not match. Input: g: GeoRegion Output: w: Wine Relationship: THERE IS SOME s: ( s: Shop & s LocatedIn g & s Sells w ) Input: g: GeoRegion Output: w: Wine Relationship: THERE IS SOME s: ( s: Shop & s LocatedIn g & s Sells w ) A service request Q 2 : a user is looking for a service that returns the french wines produced in a given french region: Note: here, the service S matches Q 2, but in “standard” approaches it (mistakenly) does not, since the outputs of S ( Wine s) are broader than the user desires ( FrenchWine s). Input: g: FrenchGeoRegion Output: w: FrenchWine Relationship: THERE IS SOME f: f: WineGrower & f LocatedIn g & f Produces w Input: g: FrenchGeoRegion Output: w: FrenchWine Relationship: THERE IS SOME f: f: WineGrower & f LocatedIn g & f Produces w Service request Services repository Service matchmaker DL Reasoner Ontology Results: Service 1 Service 2 …………