Composing Web Services on the Semantic Web by Brahim Medjahed

1. Composing Web Serviceson the Semantic Webby Brahim Medjahed Presented by Dohan Kim Lichun Zhu

2. Outline • Semantic Description of Web Services • Composability Model for Web Services • Automatic Composition of Web Services • Summarization and Conclusion

3. Semantic Description of Web Services • Web Services Description Language (WSDL) • Extending WSDL with Semantic Capabilities • Providers, Composers, and Consumers • Automatic Composition of Web Services • The approach for combining the concepts of Web Services and Ontology

4. Ontology-based description of Web Services ( WSDL Concept) Binding Name Input 1:N 1:{0,1} 1:N 1:1 Parameter Service Operation Output 1:N 1:{0,1} 1:N Data Type 1:1 1:1 1:1 Name Name

5. Semantic Description of Web Services • Mode • Notification, One-way, • Solicit-response, Request-response • Message • A Message M is defined as a tuple ( P, T, U, R ) • P is a set of parameter names • T: P → DataTypes • U: P → Units • R: P → Roles

6. Ontology-based description of Web Services ( Revisited) Mode Business Role Binding 1:1 Name Input 1:1 1:N 1:N 1:{0,1} 1:1 Parameter Service Operation Output 1:N 1:{0,1} 1:N Data Type 1:1 1:1 1:1 1:1 Name Name Unit

7. Semantic Description of Web Services • Purpose • Function, Synonyms, Specialization • Function : Business functionality defined within a given taxonomy • Synonyms : A set of alternative function names • Specialization : A set of characteristics of an operation’s function

8. Semantic Description of Web Services • Category • Domain, Synonyms, Specialization • Domain : Area of interest defined within a given taxonomy • Synonyms : A set of alternative domains • Specialization : A set of characteristics of an operation’s domain

9. Semantic Description of Web Services • Quality • Fees, Security, Privacy • Fees : Dollar amount needed to execute an operation • Security : A boolean that specifies whether an operation’s messages are securely exchanged • Privacy : A set of input and output parameters that are not divulged to external entities

10. Ontology-based description of Web Services Domain Synonym Specialization Mode 1:N Business Role 1:1 Binding Category 1:1 Name Input 1:1 1:N 1:1 1:N 1:{0,1} 1:1 Parameter Service Operation Output 1:N 1:{0,1} 1:N Data Type 1:1 1:1 1:1 1:1 Name Description Name 1:1 Unit Description 1:1 Purpose 1:N Quality 1:1 1:1 1:N 1:1 Synonym Specialization 1:1 Function Fees Security Privacy

11. Semantic Description of Web Services • Defining Web Services and Operation • Web Service • A Web service WSi is defined by a tuple: • ( Descriptioni, OPi, Bindingsi, Purposei, Categoryi ) • Operation • An operation OPik is defined by a tuple : • ( Descriptionik, Modeik, Inik, Outik, Purposeik, Categoryik, Qualityik)

12. Composability model for Web Services • Mode and Binding Composability • Message Composability • Operation Semantics Composability • Qualitative Composability • Composition Soundness

13. Composability model for Web Services • Mode Composability • Two operations are mode composable if mode of each operation is paired as follows: • ( notification, one-way), ( one-way, notification) • ( solicit-response, request-response) • ( request-response, solicit-response) • Binding Composability • WSi =( Di, Oi, Bi, Pi, Ci ), WSj =( Dj, Oj, Bj, Pj, Cj ) • Two services are binding composable if Bi ∩ Bj ≠Ø

14. Composability model for Web Services • Message Composability • A message consists of one or more parameters, each having a certain data type • Data Type Compatible (Direct vs Indirect Compatible) • Input message of a service operation may use only a subset of the parameters of an output message • Checking data type compatibility between input and output operation • Checking Unit and Business Role between input and output operation

15. Composability model for Web Services • OPik in WSi = (Dik, Mik, Inik, Outik, Pik, Cik, Qik) • OPjl in WSj = (Djl, Mjl, Injl, Outjl, Pjl, Cjl, Qjl) • Operation Semantics Composability • Pik is compatible withPjl • Cik is compatible with Cjl • Qualitative Composability • Qik.Fees≥Qjl.Fees • (Qik .Security = true) ⇒ (Qjl.Security = true) • Qik.Privacy ⊆Qjl.Privacy

16. Composability model for Web Services • Composition Soundness • Test whether composite services provides an added value • Combining airline and hotel services • Combining airline and lemon check services ? • Composition Templates • Stored Templates • A Composition of services are sound if its template is a subgraph of a stored template

17. Automatic Composition of Web Services • Four conceptually separated phases for automatic composition of Web Services • Specification Phase • Matchmaking Phase • Selection Phase • Generation Phase

18. Automatic Composition of Web Services • Specification Phase • Composite Service Specification Language ( CSSL ) • High level description of composite services • Specification of the control flow between composite service operations • Example : CSSL - Car Broker Composite Service • <service name=“car broker”/> • <category domain=“brokerage”> • <binding name=“SOAP”/> • ........ (continued)

19. Automatic Composition of Web Services • CSSL - Car broker composite service (continued) ………. • <message name=“offer”> • <parameter name=“price” type=“float” unit=“US dollar” role=“extendedPrice”/> • <parameter name=“make” type=“string” ....../> • <parameter name=“model” type=“string” ....../> • <pararmeter name=“year” type=“gYear” ....../> • <parameter name=“mileage” type=“integer” ....../> • </message> .......

20. Automatic Composition of Web Services • CSSL - Car broker composite service (continued) ………. • <operation name=“receiveSpecialOffers” mode=“one way”/> • <input name=“offer”/> • <category domain=“automobile dealer”> • <synonyms> <synonym value=“car dealer”/></synonyms> • <purpose function=“price-sales catalogue”/> • <quality> • <fees value=0/> • ....... • </operation> • <flow source=“getPayingHistory” target=“applyForFinancing”>

21. Automatic Composition of Web Services • Matchmaking phase • Generating composition plans using a matchmaking algorithm • Mapping each operation of the composite service to one or more operations of existing service and check composability. • Example functions of the algorithm • purpose_compatible(), category_compatible(), quality_composable(), message_composable(), sound()

22. Automatic Composition of Web Services • Selection phase • Quality of Composition ( QoC ) parameters • Ranking, Relevance, Completeness • Composition Ranking( CT, STi ) = • Composition Relevance = • Composition Completeness = • Plans with the highest ranking are returned first

23. Automatic Composition of Web Services • Generation phase • Generating a detailed description of a composite service • List of outsourced services • Mapping between composite and component service operations • Mapping between messages and parameters • Flow of control and data between component services • Target language for CSSL specification • Web Service Flow Language( WSFL), XLANG, etc

24. Target Language Example ( WSFL )

25. Conclusion • Automatically generate composite services from high-level specifications of the desired composition • Semantic description of Web Services • Mode, Message, Operation,Purpose, Category, etc. • Composability model for Web Services • Automatic Composition of Web Services • Specification, Matchmaking, Selection and Generation Phase

26. Questions and Answers Thank You !