 Copyright 2005 Digital Enterprise Research Institute. All rights reserved. Semantic Web Services and User Goal definition problems Andrej Hol úbek DIKE,VŠE Prague, Czech Republic, October 2007

2 Content Web services Semantic Web servicies WSMO (Web Services Modelling Ontology) User Goal definitions problems Solutions of Goal definitions

 Copyright 2005 Digital Enterprise Research Institute. All rights reserved. Web services WS

4 Web service What is web service –a program programmatically accessible over standard internet protocols –loosely coupled, reusable components –distributed over the internet –add new level of functionality on top of the current web

5 Web Services Framework

6 UDDI –Universal Description, Discovery and Integration WSDL –Web Service Definition Language SOAP –Simple Object Access Protocol

7 Web service Problems: –syntactic descriptions –discovery, composition and invocation have to be carried out by humans –scalability problems

8 Web services Vision –In U.S. Web Services Market Analysis, 2002 IDC predicts that Web services will become the dominant distributed computing architecture in the next 10 years. Web services will drive software, services and hardware sales of $21 billion in the U.S. by 2007 and will reach $27 billion in –Web services promise easy access to remote content and application functionality, independently of the provider's platform, the location, the service implementation, or the data format. Kuassi Mensah, Oracle –Exposure of capabilities

 Copyright 2005 Digital Enterprise Research Institute. All rights reserved. Semantic Web Services SWS

10 SWS Vision Web (URI, HTML, HTTP) Web Services (UDDI, WSDL, SOAP) Semantic Web (RDF, OWL) Semantic Web Services Dynamic Static Syntax Semantics

11 Semantic Web Services Semantic Web Technology –Machine readable data –Ontological basis Applied to Web Services Technology –Reusable computational resources

12 SWS Activities Usage Process: Publication: Make available the description of the capability of a service Discovery: Locate different services suitable for a given task Selection: Choose the most appropriate services among the available ones Composition: Combine services to achieve a goal Mediation: Solve mismatches (data, protocol, process) among the combined Execution: Invoke services following programmatic conventions

13 SWS Activities Execution support: Monitoring: Control the execution process Compensation: Provide transactional support and undo or mitigate unwanted effects Replacement: Facilitate the substitution of services by equivalent ones Auditing: Verify that service execution occurred in the expected way

 Copyright 2005 Digital Enterprise Research Institute. All rights reserved. Web Service Modeling Ontology WSMO

15 WSMO WSMO defines: –conceptual model for Semantic Web Services –requirements for Web Service Modelling Language (WSML) –framework for architecture and execution enviroment (WSMX)

16 WSMO Working Groups A Conceptual Model for SWS A Formal Language for WSMO A Rule-based Language for SWS Execution Environment for WSMO

17 WSMO Design Principles Web Compliance Ontology-Based Strict Decoupling Centrality of Mediation Ontological Role Separation Description versus Implementation Execution Semantics

18 WSMO Top Level Notions Objectives that a client wants to achieve by using Web Services Semantic description of Web Services: - Capability (functional) - Interfaces (usage) Connectors between components with mediation facilities for handling heterogeneities Provide the formally specified terminology of the information used by all other components

19 Non-Functional Properties every WSMO elements is described by properties that contain relevant, non-functional aspects Dublin Core Metadata Set: –complete item description –used for resource management Versioning Information –evolution support Quality of Service Information –availability, stability Other –Owner, financial

20 Non-Functional Properties List Dublin Core Metadata Contributor Coverage Creator Description Format Identifier Language Publisher Relation Rights Source Subject Title Type Quality of Service Accuracy NetworkRelatedQoS Performance Reliability Robustness Scalability Security Transactional Trust Other Financial Owner TypeOfMatch Version

21 WSMO Ontologies Provide the formally specified terminology of the information used by all other components Semantic description of Web Services: - Capability (functional) - Interfaces (usage) Connectors between components with mediation facilities for handling heterogeneities Objectives that a client wants to achieve by using Web Services

22 Ontology Usage & Principles Ontologies are used as the ‘data model’ throughout WSMO –all WSMO element descriptions rely on ontologies –all data interchanged in Web Service usage are ontologies –Semantic information processing & ontology reasoning WSMO Ontology Language WSML –conceptual syntax for describing WSMO elements –logical language for axiomatic expressions (WSML Layering) WSMO Ontology Design –Modularization: import / re-using ontologies, modular approach for ontology design –De-Coupling: heterogeneity handled by OO Mediators

23 Ontology Specification Non functional properties (see before) Imported Ontologies importing existing ontologies where no heterogeneities arise Used mediators OO Mediators (ontology import with terminology mismatch handling) Ontology Elements: Concepts set of concepts that belong to the ontology, incl. Attributes set of attributes that belong to a concept Relations define interrelations between several concepts Functions special type of relation (unary range = return value) Instances set of instances that belong to the represented ontology Axiomsaxiomatic expressions in ontology (logical statement)

24 WSMO Web Services Provide the formally specified terminology of the information used by all other components Semantic description of Web Services: - Capability (functional) - Interfaces (usage) Connectors between components with mediation facilities for handling heterogeneities Objectives that a client wants to achieve by using Web Services

25 Capability Specification Non functional properties Imported Ontologies Used mediators –OO Mediator: importing ontologies with mismatch resolution –WG Mediator: link to a Goal wherefore service is not usable a priori Pre-conditions What a web service expects in order to be able to provide its service. They define conditions over the input. Assumptions Conditions on the state of the world that has to hold before the Web Service can be executed Post-conditions describes the result of the Web Service in relation to the input, and conditions on it Effects Conditions on the state of the world that hold after execution of the Web Service (i.e. changes in the state of the world)

26 WSMO Web Service Description Web Service Implementation (not of interest in Web Service Description) Choreography --- Service Interfaces --- Capability functional description WS - Advertising of Web Service - Support for WS Discovery client-service interaction interface for consuming WS - External Visible Behavior - Communication Structure - ‘Grounding’ realization of functionality by aggregating other Web Services - functional decomposition - WS composition Non-functional Properties DC + QoS + Version + financial - complete item description - quality aspects - Web Service Management WS Orchestration

27 Choreography and Orchestration VTA Service Date Time Flight, Hotel Error Confirmation Hotel Service Flight Service Date, Time Hotel Error Date, Time Flight Error When the service is requested When the service requests VTA example: Choreography = how to interact with the service to consume its functionality Orchestration = how service functionality is achieved by aggregating other Web Services

28 WSMO Mediators Provide the formally specified terminology of the information used by all other components Semantic description of Web Services: - Capability (functional) - Interfaces (usage) Connectors between components with mediation facilities for handling heterogeneities Objectives that a client wants to achieve by using Web Services

29 Mediation Heterogeneity … –For 1$ on programming, $5 - $9 on integration –Mismatches on structural / semantic / conceptual / level –Assume (nearly) always necessary Description of role –Components that resolve mismatches –Declarative description of arbitrary web service Types of Mediation within Semantic Web Services: (1) Data: mediate heterogeneous Data Sources (2) Protocol: mediate heterogeneous Communication Patterns (3) Process: mediate heterogeneous Business Processes

30 WSMO Mediators Overview

31 WSMO Goals Provide the formally specified terminology of the information used by all other components Semantic description of Web Services: - Capability (functional) - Interfaces (usage) Connectors between components with mediation facilities for handling heterogeneities Objectives that a client wants to achieve by using Web Services

32 Goals Ontological De-coupling of Requester and Provider Derived from task / problem solving methods/domain model Structure and reuse of requests –Search –Diagnose –Classify –Personalise –Book a holiday Requests may in principle not be satisfiable Ontological relationships & mediators used to link goals to web services

33 Goal Specification Non functional properties Imported Ontologies Used mediators –OO Mediators: importing ontologies with heterogeneity resolution –GG Mediator: Goal definition by reusing an already existing goal allows definition of Goal Ontologies Requested Capability –describes service functionality expected to resolve the objective –defined as capability description from the requester perspective Requested Interface –describes communication behaviour supported by the requester for consuming a Web Service (Choreography) –Restrictions / preferences on orchestrations of acceptable Web Services

 Copyright 2005 Digital Enterprise Research Institute. All rights reserved. User Goal definitions problems

35 User View of Goal User Goal definition Middleware Service1 Service2

36 Goal definition WSML Goal –Non-functional properties –Preconditions Person (name, company) Caller (userPart, domain) –Postconditions Callee (userPart, domain) –Effect callAuthorized(caller, callee)

37 User View of Goal User Goal definition Middleware Service1 Service2 User friendly definition

38 User friendly definition Solutions The SemanticGov portal –Nikos Loutas, Vassilios Peristeras Goal-based Visualization and Browsing for Semantic Web Services –Michael Stollberg, Mick Kerrigan Towards Specifying User needs as a Formal Goal –Andrej Holúbek

39 The SemanticGov portal The aim of the discovery process is to capture the citizen’s need and to help track down the service instance that address need starting from an abstract service type and going down a tree-like structure. Tree like structure is a service ontology (called service tree ontology) that describes the specific service type The basic idea of the tree-structure is that the leaves are the specific service instances, while the internal nodes are the different service sub-type, which become more and more specific (and finally end up in service instances) as we go down the tree.

40 The SemanticGov portal

41 Goal-based Visualization and Browsing for Semantic Web Services It is a goal-based graphical user interface for visualizing and browsing the search space of available Web services. The visualization technique is based on graph structure that organizes goal templates with respect to their semantic similarity, and keeps the relevant knowledge on the available Web services for solving them. The graph is generated automatically from the results of semantically enabled Web service discovery. It present novel approach for the visualization and browsing of Web services that allows clients to comprehend and inspect available Web services on the level of problems that can be solved by them, abstracting from the technical details.

42 Goal-based Visualization and Browsing for Semantic Web Services SDC Graph Visualization in WSMT

43 Towards Specifying User needs as a Formal Goal This solution is based on expert system using knowledge base Knowledge base is created from available services, its conditions and expert grouping knowledge. Knowledge base will contain 3 levels. –First ground level will contain nodes as representation of available services expressed in WSML. – In second level expert will create nodes as list of services which fulfil one goal (e.g.: hotel reservation, citizenship registration …). In this level nodes will contain order list of services fulfilling one goal step by step –(e.g.: hotel reservation = find hotels in specific area ->select one hotel-> check availability in specific date -> reserve selected room). In this level specific data will be collected from user asking relevant questions. –In third level goals will be grouped to specific groups that represent those goals (e.g.: hotel reservation, booking ticket, renting car … => planning trip; => travelling...). In this level questions will be asked to specified area of interesting.

44 Schema of Knowledge base All available services Specific goals Specific area root Traveling Government services Free time activities Bussines Trade Registrations CitizenshipDriving licence Visa BuyingSelling Tickets Bus Reservation Find Bus Companies Find Bus Link Buy Bus Ticket Level 1 Level 2 Level 3 Bus Ticket

45 Process of building goal UserInterfaceExpert System Propose the specific area Choose the specific area Select the specific goal Graph of specific areas List of services for specific goal Ask for concrete data Give the concrete data Get the concrete data Execute the services Give results to user

46 Summary Web Services are –Reusable programs available over the web –Match business services Semantic web services –Applies semantic web technology to web services WSMO –Ontology, Goal, Web Service and Mediator –Ontological separation of requester and provider context User Goal problems –Needs of knowledge of specific language –Non-friendly user goal definition

47 References The central location where WSMO work and papers can be found is WSMO Working Group: Andrej Holúbek, Towards Specifying User needs as a Formal Goal, September 2007 N. Loutas and V. Peristeras, The SemanticGov portal M. Stollberg and M. Kerrigan, Goal-based Visualization and Browsing for Semantic Web Services, 2007 Web Service Modeling Ontology Primer. Available at June Web Service Modeling Language (WSML), Available at June T. Vitvar and J. Viskova,Semantic-enabled Voice and Data Integration: Telecommunication Use Case,2005 John Domingue, Semantic Web Services: The Web Service Modelling Ontology and IRS-III, 2005