Understanding Service-Oriented Computing in Web Environments

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

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

3. 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 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

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 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

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 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

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. Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

7. Brief History of Information Technology Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

8. System Architectures: Centralized Terminal 3270 Terminal Terminal Terminal Terminal Mainframe Terminal Terminal Terminal Terminal Terminal Terminal Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

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

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

11. 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) Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

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 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

13. 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 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

14. 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 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

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 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

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 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

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 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

18. Historical View of Services over the Web Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

19. 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 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

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 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

21. 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 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns