1 Composing Web Services on the Semantic Web by 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 Service Binding Name Ontology-based description of Web Services ( WSDL Concept) Operation Input Output Name Parameter Name Data Type 1:N 1:1 1:{0,1}

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

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 Service Binding Name Ontology-based description of Web Services Operation Input Output Name Parameter Name Data Type 1:N 1:1 1:{0,1} Mode Unit Business Role 1:1 Purpose Category Function SynonymSpecialization DomainSynonymSpecialization Quality FeesSecurityPrivacy Description 1:1 1:N 1:1 1:N

11 Semantic Description of Web Services Defining Web Services and Operation Web Service  A Web service WS i is defined by a tuple:  ( Description i, OP i, Bindings i, Purpose i, Category i ) Operation  An operation OP ik is defined by a tuple :  ( Description ik, Mode ik, In ik, Out ik, Purpose ik, Category ik, Quality ik )

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  WS i =( D i, O i, B i, P i, C i ), WS j =( D j, O j, B j, P j, C j )  Two services are binding composable if B i ∩ B j ≠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  OP ik in WS i = (D ik, M ik, In ik, Out ik, P ik, C ik, Q ik )  OP jl in WS j = (D jl, M jl, In jl, Out jl, P jl, C jl, Q jl ) Operation Semantics Composability  P ik is compatible with P jl  C ik is compatible with C jl Qualitative Composability  Q ik.Fees ≥ Q jl.Fees  (Q ik.Security = true) ⇒ (Q jl.Security = true)  Q ik.Privacy ⊆ Q jl. 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   (continued)

19 Automatic Composition of Web Services CSSL - Car broker composite service (continued) ………. 

20 Automatic Composition of Web Services CSSL - Car broker composite service (continued) ……….   

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, ST i ) =  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 !