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 Syntax, Language, and Vocabulary - FIPA ACL Semantics and Understanding - Ontologies, OWL Pragmatics (getting work done) - Workflows, BPEL4WS Distributed Cognition - Decisions and Plans Current Web Services: focus on individual and small group Future Web Services: focus on organization and society

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 Viewpoints on Services Networking: a service is characterized by bandwidth and suchlike properties. Telecommunications: Narrow telephony features such as caller ID and call forwarding, and basic connection services like narrowband versus broadband (itself of a few varieties). Systems: Services are for billing and storage and other key operational functions. These functions are often parceled up in the so-called operation-support systems. Web applications: Services correspond to Web pages, especially those with forms or a programmatic interface thereto. Wireless: Wireless versions of the Web, but also things like messaging, as in the popular short message service (SMS). If there is agreement here, it is that a service is a capability that is provided and exploited, often but not always remotely.

7 Brief History of Information Technology

8 System Architectures: Centralized Mainframe Terminal3270 Terminal

9 System Architectures: Client-Server Server Web Server Database Server PC Client PC Client PC Client Workstation Client Master-Slave

10 System Architectures: Peer-to-Peer System Web System Database System Application

11 System Architectures: Cooperative System Web System Database System Application (Mediators, Proxies, Aides, Wrappers) Agent

12 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

13 (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

14 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

15 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

16 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

17 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

18 (3) Services Introduced Historical View of Services over the Web GenerationScopeTechnologyExample FirstAllBrowserAny HTML page SecondProgrammaticScreen scraper Systematically generated HTML content ThirdStandardizedWeb servicesFormally described service FourthSemanticSemantic Web services Semantically described service

19 (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

20 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

21 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

22 (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)

23 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

24 Standards for Web Services

25 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

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

27 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