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Computing with Services CS 696 – Services Computing Fall 2008

Computing with Services CS 696 – Services Computing Fall 2008. Chapter 1, Service-Oriented Computing: Semantics, Processes, Agents – Munindar P. Singh and Michael N. Huhns, Wiley, 2005. Highlights of this Chapter. (1) Visions for the Web (2) Open Environments (3) Services Introduced

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Computing with Services CS 696 – Services Computing Fall 2008

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  1. Computing with Services CS 696 – Services Computing Fall 2008 Chapter 1, Service-Oriented Computing: Semantics, Processes, Agents– Munindar P. Singh and Michael N. Huhns, Wiley, 2005

  2. Highlights of this Chapter (1) Visions for the Web (2) Open Environments (3) Services Introduced (4) The Evolving Web (5) Standards Bodies

  3. (1) Visions for the Web- The Web As Is • Designed for people to get information • Sources are independent and heterogeneous • Limitations • HTML describes how things appear • HTTP is stateless • Processing is asynchronous client-server • No support for integrating information • No support for meaning and understanding

  4. Web Semantics • “The Semantic Web” is Tim Berners-Lee’s vision • Human  Machine  Agents • Client-Server  P2P  Cooperative • Syntax  Semantics  Mutual Understanding  Pragmatics and Cognition • Data  Services  Processes Future Web Services: focus on organization and society Pragmatics (getting work done) - Workflows, BPEL4WS Distributed Cognition - Decisions and Plans Semantics and Understanding - Ontologies, OWL Syntax, Language, and Vocabulary - FIPA ACL Current Web Services: focus on individual and small group

  5. What is a Web Service? • "… a piece of business logic accessible via the Internet using open standards…“ (Microsoft) • Encapsulated, loosely coupled, contracted software functions, offered via standard protocols over the web (DestiCorp) • A set of interfaces, which provide a standard means of interoperating between different software applications, running on a variety of platforms and/or frameworks (W3C) Our working definition: A WS is functionality that can be engaged over the Web

  6. Brief History of Information Technology

  7. System Architectures: Centralized Terminal 3270 Terminal Terminal Terminal Terminal Mainframe Terminal Terminal Terminal Terminal Terminal Terminal

  8. System Architectures: Client-Server Workstation Client PC Client PC Client PC Client E-Mail Server Web Server Database Server Master-Slave

  9. System Architectures: Peer-to-Peer Application Application Application Application E-Mail System Web System Database System

  10. System Architectures: Cooperative Agent Application Application Application Agent Agent Agent Application Agent Agent E-Mail System Agent Agent Database System Web System (Mediators, Proxies, Aides, Wrappers)

  11. Kinds of Networks • Internet • Intranet: network restricted within an enterprise • Extranet: private network restricted to selected enterprises • Virtual Private Network (VPN): a way to realize an intranet or extranet over the Internet When we talk about Internet computing or Web services, we consider all of the above as possible environments

  12. (2) Open Environments- Characteristics • Cross enterprise boundaries or administrative domains • Comprise autonomous resources that • Involve loosely structured addition and removal • Range from weak to subtle consistency requirements • Involve updates only under local control • Frequently involve nonstandard data • Have intricate interdependencies

  13. Autonomy (Usage) • The Components in an environment function solely under their own control. Independence of business partners (users) • Political reasons • Ownership of resources • Control, especially of access privileges • Payments • Technical reasons • Opacity of systems with respect to key features, e.g., precommit

  14. Heterogeneity (Construction) Independence of component designers and system architects • Political reasons • Ownership of resources • Technical reasons • Conceptual problems in integration • Fragility of integration • Difficult to guarantee behavior of integrated systems Best not to assume homogeneity

  15. Dynamism (Configuration) • Independence of system administrators • Needed because the parties change • Architecture and implementation • Behavior • Interactions • Make configurations dynamic to improve service quality and maintain flexibility

  16. Locality • Global information (data, schemas, constraints) causes • Inconsistencies • Anomalies • Difficulties in maintenance • Global information is essential for coherence • Locations of services or agents • Applicable business rules • Relaxation of constraints works often • Obtain other global knowledge only when needed • Correct rather than prevent violations of constraints: often feasible • When, where, and how of corrections must be specified, but it is easier to make it local

  17. (3) Services IntroducedHistorical View of Services over the Web

  18. (4) The Evolving Web • Near Web: conventional mouse-keyboard-monitor interaction with a personal computer, typically for purposes such as surfing the Web • Far Web: interaction with a computer from across a room as with a TV remote control, typically for entertainment, such as listening to music or viewing a movie • Here Web: interaction with a mobile device, with narrow bandwidths for input and output

  19. The Evolving Web (conti) • Weird Web: interaction through emerging interface technologies, such as voice and wearable computing • B2B Web: dealing with the supply networks of business-to-business electronic commerce • Pervasive Web: dealing with device-to-device interactions

  20. Applications of Services • Services should be composable • Provided independently • Used in novel, unanticipated ways • Portals • Organized by topic or affinity • Best when personalized • E-commerce • Legacy system integration • Virtual enterprises • Grid computing

  21. (5) Standards Bodies • The following are the most important stanards bodies and initiatives for services. • IETF – The Internet Engineering Task Force TCP/IP Suite and URIs, HTTP, SIP, SMTP • OMG – The Object Management Group UML, CORBA, MDA • W3C – The World Wide Web Consortium XML, XML Schema, WSDL, SOAP, and WSCI • OASIS – The Organization for the Advancement of Structured Information Standards Universal Business Language (UBL), UDDI, and the Business Process Execution Language for Web Services (BPEL4WS)

  22. Standards Bodies (Conti) • UN/CEFACT – The United Nations Center for Trade Facilitation and Electronic Business - ebXML • WS-L – The Web Services Interoperability Organization - BP 1.0 • BPMLorg - The Business Process Management Initiative - Business Process Modeling Language (BPML) • WfMC - The Workflow Management Coalition • FIPA – The Foundation for Intelligent Physical Agents promotes technologies and specifications

  23. Standards for Web Services

  24. XML Web Service Foundation Open and with broad industry support • Publish, Find, Use Services • UDDI • Service Interactions • SOAP • Universal Data Format • XML • Description Language • WSDL • Ubiquitous Communications • TCP/IP, HTTP, SMTP, SIP, Reliable messaging • Security (authentication and authorization) • WS-Security, SAML

  25. eXtensible Markup Language (XML) • Simple Object Access Protocol (SOAP) • Web Services Description Language (WSDL) • Directory Services • Universal Description, Discovery, and Integration (UDDI)

  26. Summary • Evolving perspectives on the Web • Evolutions in IT architectures • Key aspects of open environments • Autonomy • Heterogeneity • Dynamism • Services, if understood correctly, can support IT in open environments

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