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

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Presentation on theme: "Chapter 1: Computing with Services Service-Oriented Computing: Semantics, Processes, Agents – Munindar P. Singh and Michael N. Huhns, Wiley, 2005."— Presentation transcript:

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

2 Chapter 12Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Highlights of this Chapter Visions for the Web Open Environments Services Introduced The Evolving Web Standards Bodies

3 Chapter 13Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 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 Chapter 14Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Web Semantics The Semantic Web is Tim Berners-Lees 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 Chapter 15Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 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 Chapter 16Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 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 Chapter 17Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Brief History of Information Technology

8 Chapter 18Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns System Architectures: Centralized Mainframe Terminal3270 Terminal

9 Chapter 19Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns System Architectures: Client-Server Server Web Server Database Server PC Client PC Client PC Client Workstation Client Master-Slave

10 Chapter 110Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns System Architectures: Peer-to-Peer System Web System Database System Application

11 Chapter 111Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns System Architectures: Cooperative System Web System Database System Application (Mediators, Proxies, Aides, Wrappers) Agent

12 Chapter 112Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 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 Chapter 113Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 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 Chapter 114Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Autonomy (Usage) 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 Chapter 115Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 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 Chapter 116Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 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 Chapter 117Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 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 Chapter 118Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 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 Chapter 119Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 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 Weird Web: interaction through emerging interface technologies, such as voice and wearable computing

20 Chapter 120Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 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 Chapter 121Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Chapter 1 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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