Adding Semantics to Web Services Standards

1. Adding Semantics to Web Services Standards Kaarthik Sivashanmugam, Kunal Verma, Amit Sheth and John Miller LSDIS Lab, Department of Computer Science The University of Georgia

2. Outline • Challenges in web services adoption • Web services conceptual stack and semantics at different layers • Semantics for web service usage lifecycle • METEOR-S project at LSDIS lab • Semantic publication and discovery of web services • Conclusion, References and Q&A

3. Web Service Conceptual Stack1 Description Messaging Network • Description:Web Service Description Language (WSDL) • To describe Web Service interfaces and implementations • Details in WSDL files (data types, operations, binding details, access location) are used for service invocation • Messaging:(SOAP) • XML based messaging protocol • Network:(HTTP) • Network protocol 1 [Kreger]

4. Web Service Conceptual Stack1 Discovery Publication Description Messaging Network • Publication:(UDDI) • To make service descriptions available for search • Discovery:(UDDI) • To locate service descriptions Flow • Flow:(BPEL4WS, WSCI etc.) • To compose web services to form a composite web service / process 1 [Kreger]

5. BIG Challenges • Machine understandable descriptions • Dynamic discovery and service selection • Scalability in discovery mechanisms Hypothesis: Semantics is the most important enabler

6. METEOR-S at LSDIS lab • Adding semantics to different layers of Web services conceptual stack • Applying* semantic Web techniques to industry accepted Web services standards for better Web service description • to solve the problems of scalability and heterogeneity in Web service discovery, selection and composition * Use of ontologies to provide underpinning for information sharing and semantic interoperability

7. Semantics at Different Layers Discovery Publication • Description Layer: • Why: • Reason about the functionality of the services and the semantics of the operational data • How: • Using Ontologies to semantically annotate WSDL constructs (conforming to extensibility allowed in WSDL specification version 1.2) to sufficiently explicate the semantics of the • data types used in the service description and • functionality of the service • Present scenario: • WSDL descriptions are mainly syntactic (provides operational information and not functional information) • Semantic matchmaking is not possible Flow Description Messaging Network

8. Semantics at Different Layers (contd..) Discovery Publication • Publication and Discovery Layers: • Why: • Enable scalable, efficient and dynamic publication and discovery (machine processability / automation) • How: • Use of ontology to categorize registries based on domains and characterize them by maintaining the • properties of each registry • relationships between the registries • Capturing the WSDL annotations in UDDI • Present scenario: • Suitable for simple searches ( like services offered by a provider, services that implement an interface, services that have a common technical fingerprint etc.) • Categories are too broad • Automated service discovery (based on functionality) and selecting the best suited service is not possible Flow Description Messaging Network

9. Semantics at Different Layers (contd..) Discovery Publication • Flow Layer: • Why: • Design (composition), analysis (verification), validation (simulation) and execution (exception handling) of the process models • To employ mediator architectures for automated composition, control flow and data flow based on requirements • How: • Using • Functionality/preconditions/effects of the participating services • Knowledge of conversation patterns supported by the service • Formal mathematical models like process algebra • Simulation techniques • Present Scenario: • Composition of Web services is static. • Dynamic service discovery, run-time binding, analysis and simulation are not supported directly Flow Description Messaging Network

10. Semantics in METEOR-S Discovery Publication MWSCF: Semantic Web Process Composition Framework Flow MWSDI: Scalable Infrastructure of Registries for Semantic publication and discovery of Web Services Description MWSDI: Semantic Annotation of WSDL (WSDL-S) Messaging Network

11. Scope of Semantic Web with respect to Web Services Current Semantic Web Focus Formal Semantic Web Processes Semi-Formal Degree of Agreement Agreement About Qos Informal Execution Scope of Agreement Function Common Sense Gen. Purpose,Broad Based Domain Industry Data/ Info. Task/ App Lots of Useful Semantic Technology (interoperability, Integration) Other dimensions: how agreements are reached, …

12. Semantics for Web Services • Data/Information Semantics • Formal definition of data in input and output messages of a web service • for discovery and interoperability • by annotating input/output data of web services using ontologies • Functional/Operational Semantics • Formally representing capabilities of web service • for discovery and composition of Web Services • by annotating operations of Web Services as well as provide preconditions and effects; Annotating TPA/SLA • Execution Semantics • Formally representing the execution or flow of a services in a process or operations in a service • for analysis (verification), validation (simulation) and execution (exception handling) of the process models • using State Machines, Petri nets, activity diagrams etc. • QoS Semantics • Formally describing operational metrics of a web service/process • To select the most suitable service to carry out an activity in a process • using QoS model [Cardoso and Sheth, 2002] for web services

13. Semantics for Web Service usage life cycle Execution Development / Description / Annotation WSDL, WSEL DAML-S Meteor-S (WSDL Annotation) BPWS4J, Commercial BPEL Execution Engines, Intalio n3, HP eFlow BPEL, BPML, WSCI, WSCL, DAML-S, METEOR-S (SCET,SPTB) UDDI WSIL, DAML-S METEOR-S (P2P model of registries) Composition Publication / Discovery Data / Information Semantics

14. Semantics for Web Service usage life cycle Execution Development / Description / Annotation WSDL, WSEL DAML-S Meteor-S (WSDL Annotation) BPWS4J, Commercial BPEL Execution Engines, Intalio n3, HP eFlow Data / Information Semantics BPEL, BPML, WSCI, WSCL, DAML-S, METEOR-S (SCET,SPTB) UDDI WSIL, DAML-S METEOR-S (P2P model of registries) Composition Publication / Discovery

15. Semantics for Web Service usage life cycle Execution Development / Description / Annotation WSDL, WSEL DAML-S Meteor-S (WSDL Annotation) BPWS4J, Commercial BPEL Execution Engines, Intalio n3, HP eFlow Functional / Operational Semantics BPEL, BPML, WSCI, WSCL, DAML-S, METEOR-S (SCET,SPTB) UDDI WSIL, DAML-S METEOR-S (P2P model of registries) Composition Publication / Discovery

16. Semantics for Web Service usage life cycle Execution Development / Description / Annotation WSDL, WSEL DAML-S Meteor-S (WSDL Annotation) BPWS4J, Commercial BPEL Execution Engines, Intalio n3, HP eFlow QoS Semantics BPEL, BPML, WSCI, WSCL, DAML-S, METEOR-S (SCET,SPTB) UDDI WSIL, DAML-S METEOR-S (P2P model of registries) Composition Publication / Discovery

17. Semantics for Web Service usage life cycle Execution Development / Description / Annotation WSDL, WSEL DAML-S Meteor-S (WSDL Annotation) BPWS4J, Commercial BPEL Execution Engines, Intalio n3, HP eFlow Execution Semantics BPEL, BPML, WSCI, WSCL, DAML-S, METEOR-S (SCET,SPTB) UDDI WSIL, DAML-S METEOR-S (P2P model of registries) Composition Publication / Discovery

18. Semantics for Web Service usage life cycle Execution Semantics Data / Information Semantics QoS Semantics Functional / Operational Semantics Execution Development / Description / Annotation WSDL, WSEL DAML-S Meteor-S (WSDL Annotation) BPWS4J, Commercial BPEL Execution Engines, Intalio n3, HP eFlow Semantics Required for Web Processes BPEL, BPML, WSCI, WSCL, DAML-S, METEOR-S (SCET, SPTB) UDDI WSIL, DAML-S METEOR-S (P2P model of registries) Composition Publication / Discovery

19. METEOR-S components for Semantic Web Services • Discovery Infrastructure (MWSDI) • Semantic Annotation of Web Services1 • Semantic Peer-to-Peer network of Web Services Registries 2 • Composer • SCET: Service Composition and Execution Tool 3 • Semantics process template builder and Process generator 4 • QoS Management • Specify, compute, monitor and control QoS (SWR algorithm) 5 • Orchestrator(Under development) • Analysis and Simulation6 • Execution • Monitoring6 • 1 [Sivashanmugam et al.-1], 2 [Verma et al.], 3 [Chandrasekaran et al.], 4 [Sivashanmugam et al.-2], • 5 [Cardoso et al.], 6 [Silver et al.]

20. Search for services to book air ticket (using categories)* • unspsc-org: unspsc:3-1 • Travel, Food, Lodging and Entertainment Services • Travel facilitation • Travel agents • Travel agencies • Services: 3 records found. • AirFares Returns air fares from netviagens.com travel agent • Hotel reservations Reservations for hotels in Asia, Australia and New Zealand • Your Vacation Specialists Web enabled vacation information • Providers: 2 records found. * Search carried out in one of the Universal Business Registries

21. Search for services to book air ticket (using keywords)* • air ticket • 1 record with name air tickets booking • airticket, ticketbooking, airtravel, air travel, travel agent, airticketbooking, air ticket booking, travel agency, travelagency • 0 records were returned • travelagent • 1 record with name travelagent test • 4 services: BookFlight, cancelFlightBooking etc. • Descriptions say that both these services are “XML based Web services” • No URL for WSDL • Travel • 15 records. Purpose/functionality understood from descriptions • 2 services : TravelBooks • 4 services : TravelInformation • 2 services : Reservation and cancallation of travel tickets • 1 service : Emergency Services for travellers • 1 service : Travel documentation and itinerary • 5 services : Description is ambiguous/not present * Search carried out in one of the Universal Business Registries

22. Semantic Discovery: Overview • Annotation and Publication • WSDL file is annotated using ontologies and the annotations are captured in UDDI • Discovery • Requirements are captured as templates that are constructed using ontologies and semantic matching is done against UDDI entries • Functionality of the template, its inputs, outputs, preconditions and effects are represented using ontologies • Use of ontologies • brings service provider and service requestor to a common conceptual space • helps in semantic matching of requirements and specifications

23. Semantic Publication and Discovery Use of ontologies enables shared understanding between the service provider and service requestor For simplicity of depicting, the ontology is shown with classes for both operation and data

24. WSDL-S (WSDL with Semantic Annotation) • Mapping Input and Output Message Parts to Ontology • XML Schema elements used in Input/Output messages do not reflect the semantics of the data involved in Web Service operation • Use of ontologies or standard vocabulary* brings service provider and requestor to common conceptual space providing well defined semantics for operational data • Mapping Operations to Ontology • Service selection involves discovering appropriate WSDL description and locating an operation to invoke • Operations with same signature could have different functionalities • Ontology or vocabulary depicting functionality is used for annotation • Additional tags to represent pre-conditions and effects of each operation • Preconditions and effects are added for each operation • Can be optionally used for service discovery and selection *RosettaNet Business/Technical dictionary or ebXML Core Component catalog/dictionary The focus of our work is not in developing ontologies for representing functionality/preconditions/effects but to use such ontologies for semantic annotation

25. Annotation Syntax* • Each Operation in WSDL is annotated using an fully qualified attribute name-value pair in the operation element under portType element. The attribute name is operation-concept • Each Message part is annotated using a fully qualified attribute name-value pair in the part element under message element. The attribute name is onto-concept • Preconditions and effects are respectively represented using fully qualified additional tags with the names precondition and effect. These elements have two attributes name (optional) and precondition-concept (or effect-concept). Each operation can have multiple precondition and effectelements. * conforms to extensibility support in WSDL version 1.2

26. WSDL Annotation Example <?xml version="1.0" encoding="UTF-8"?> <wsdl:definitions xmlns:LSDISOnt=lsdis.cs.uga.edu//METEORS/TravelServiceOntology.daml ….. > <wsdl:message name="OperationRequest"> <wsdl:part name="in0" type="tns:TravelDetails" LSDISExt:ontoconcept= "LSDISOnt:TicketInformation"/> </wsdl:message> <wsdl:portType name="TravelArragement"> <wsdl:operation name="buyTicket" parameterOrder="in0" LSDISExt:operation-concept="LSDISOnt:TicketBooking"> <wsdl:input message="intf:OperationRequest" name="buyTicketRequest"/> <wsdl:output message="intf:OperationResponse" name="buyTicketResponse"/> <LSDISExt:precondition name="ValidCreditCard" LSDISExt:precondition-concept="LSDISOnt:ValidCreditCard"/> </wsdl:operation> </wsdl:definitions>

27. Semantics in UDDI • tModels are used to categorize and characterize service entries in UDDI (limited form of semantics) • Our approach uses categorizes* (using metadata constructs tModels and CategoryBags) the services in UDDI based on the semantic annotations * similar to [Paolucci et al.]

28. Semantic Categorization of Services in UDDI* For the example discussed earlier: Travel Arrangement Service with two operations buyTicket and cancelTicket Service CategoryBag TmodelKey:OperationalTModelKey, Value:TicketBooking, Name:buyTicket KeyedReferenceGroup (SemanticGroupTModelKey) TmodelKey:InputTModelKey, Value:TicketInformation TmodelKey:OutputTModel, Value:ConfirmationMessage KeyedReferenceGroup (SemanticGroupTModelKey) TmodelKey:OperationalTModelKey, Value:TicketCancellation, Name:cancelTicket TmodelKey:InputTModelKey, Value:TicketInformation TmodelKey:OutputTModel, Value:ConfirmationMessage * conforming to UDDI Version 3 spec [UDDI-v3]

29. Semantic Categorization of Services in UDDI* Operation-ontology mapping in WSDL for buyTicket operation <operation name=“buyTicket” operation-concept=“TravelOnto:TicketBooking”> Service CategoryBag TmodelKey:OperationalTModelKey, Value:TravelOnto:TicketBooking, Name:buyTicket KeyedReferenceGroup (SemanticGroupTModelKey) TmodelKey:InputTModelKey, Value:TravelOnto:TicketInformation TmodelKey:OutputTModelKey, Value:GeneralTradeOnto:ConfirmationMessage KeyedReferenceGroup (SemanticGroupTModelKey) TmodelKey:OperationalTModelKey, Value: TravelOnto:TicketCancellation, Name:cancelTicket TmodelKey:InputTModelKey, Value: TravelOnto:TicketInformation TmodelKey:OutputTModelKey, Value: GeneralTradeOnto: ConfirmationMessage * conforming to UDDI Version 3 spec [UDDI-v3]

30. Semantic Categorization of Services in UDDI* Input Message part-ontology mapping in WSDL for buyTicket operation <part name=“input1”type=“tns:TravelDetails” onto-concept=“TravelOnto:TicketInformation”> Service CategoryBag TmodelKey:OperationalTModelKey, Value:TicketBooking, Name:buyTicket KeyedReferenceGroup (SemanticGroupTModelKey) TmodelKey:InputTModelKey, Value:TravelOnto:TicketInformation TmodelKey:OutputTModelKey, Value: GeneralTradeOnto:ConfirmationMessage KeyedReferenceGroup (SemanticGroupTModelKey) TmodelKey:OperationalTModelKey, Value:TravelOnto:TicketCancellation, Name:cancelTicket TmodelKey:InputTModelKey, Value: GeneralTradeOnto:TicketInformation TmodelKey:OutputTModel, Value: GeneralTradeOnto:ConfirmationMessage * conforming to UDDI Version 3 spec [UDDI-v3]

31. Semantic Categorization of Services in UDDI* Output Message part-ontology mapping in WSDL for buyTicket operation <part name=“output”type=“xsd:String” onto-concept=“GeneralTradeOnto:ConfirmationMessage”> Service CategoryBag TmodelKey:OperationalTModelKey, Value:TicketBooking, Name:buyTicket KeyedReferenceGroup (SemanticGroupTModelKey) TmodelKey:InputTModelKey, Value:TravelOnto:TicketInformation TmodelKey:OutputTModelKey, Value: GeneralTradeOnto:ConfirmationMessage KeyedReferenceGroup (SemanticGroupTModelKey) TmodelKey:OperationalTModelKey, Value:TravelOnto:TicketCancellation, Name:cancelTicket TmodelKey:InputTModelKey, Value: GeneralTradeOnto:TicketInformation TmodelKey:OutputTModel, Value: GeneralTradeOnto:ConfirmationMessage * conforming to UDDI Version 3 spec [UDDI-v3]

32. Semantic Categorization of Services in UDDI* OperationalTModel InputTModel OutputTModel SemanticGroupTModel Same for all UDDI entries Service CategoryBag KeyedReferenceGroup (SemanticGroupTModel) TmodelKey:OperationalTModel, Value:OperationConcept, Name:OperationName KeyedReferenceGroup (SemanticGroupTModel) TmodelKey:InputTModel, Value:Input_Concept_W ……. KeyedReferenceGroup (SemanticGroupTModel) TmodelKey:InputTModel, Value:Input_Concept1_Y TmodelKey:OutputTModel, Value:Output_Concept_X ……. TmodelKey:OutputTModel, Value:Output_Concept1_Z * conforming to UDDI Version 3 spec

33. Discovery using UDDI API • Services are matched if their CategoryBags are a subset of the CategoryBag used in search (find_service) • According to UDDI version 3 specification CategoryBags can be constructed using KeyedReferenceGroups. So groups can be constructed using the semantics of operation, inputs, outputs, preconditions and effects and search can be carried out.

34. Discovery using UDDI API • Our implementation used UDDI Version 1 API • KeyedReferenceGroups are not supported • Each operation is grouped with its operation-concept, input and output onto-concepts each as a keyedReference in the keyedReferenceVector as tModelKey = “OpTModel” KeyValue = “operation-concept” KeyName = “OpName” tModelKey = “InTModel” KeyValue = “onto-concept” KeyName = “OpName” tModelKey = “OutTModel” KeyValue = “onto-concept” KeyName = “OpName” OpTModel: Key for the tModel representing functional semantics of the operation named “OpName” in a WSDL file linked to the UDDI entry InTModel: Key for the tModel representing semantics of the inputs of the operation named “OpName” in the WSDL OutTModel: Key for the tModel representing semantics of the outputs of the operation named “OpName” in the WSDL operation-concept: Fully qualified Id of a class in a functional ontology represented by OpTModel onto-concept: Fully qualfied Id of a class in a ontology that is used to annotate inputs (or outputs) represented by InTModel (or OutTModel)

35. Summary of Steps in Discovery • Services selection based on the functional requirements • Using operation-ontology mapping • Ranking based on semantic similarity based on input/output semantics of candidate services and requirement template • Using message part-ontology mapping • Optional step includes semantic similarity based on semantics of preconditions/effects of the candidate services and requirement template • Using precondition and effect tags

36. Conclusions • Semantics is the enabler to address the problems of scalability, heterogeneity (syntactic and semantic), machine understandability faced by Web services • Semantics can be applied to different layers of Web Services conceptual stack • Semantics for Web Services can be categorized into atleast 4 different dimensions namely Data, Functional, Execution and Quality.

37. References • [Kreger] http://www-3.ibm.com/software/solutions/webservices/pdf/WSCA.pdf • [Sivashanmugam et al.-1] Adding Semantics to Web Services Standards • [Sivashanmugam et al.-2] Framework for Semantic Web Process Composition • [Verma et al.] MWSDI: A Scalable Infrastructure of Registries for Semantic Publication and Discovery of Web Services • [Chandrasekaran et al.] Performance Analysis and Simulation of Composite Web Services • [Cardoso et al.] Modeling Quality of Service for Workflows and Web Service Processes • [Silver et al.] Modeling and Simulation of Quality of Service for Composition of Web Services • [Paolucci et al.] Importing Semantic Web in UDDI • [UDDI-v3] http://uddi.org/pubs/uddi-v3.00-published-20020719.htm

38. Thank you