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

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

Chapter 13Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns System Architectures: Centralized Mainframe Terminal3270 Terminal

Chapter 14Service-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

Chapter 15Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns The Web As It Is Not easy to program Designed for people to get information Focuses on visual display (as in HTML) Lacks support for meaning Supports low-level interactions HTTP is stateless Processing is client-server Creates avoidable dependencies among what should be independent components

Chapter 16Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns System Architectures: Peer-to-Peer Assume homogeneity System Web System Database System Application

Chapter 17Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns System Architectures: Cooperative Assume heterogeneity; agents handle interactions System Web System Database System Application (Mediators, Proxies, Aides, Wrappers) Agent

Chapter 18Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns The Web As It Is Becoming Enable interactions autonomous, heterogeneous parties (information providers and users) Go beyond visual display to capture meaning  Semantically expressive Web Support standardized interfaces  Web services Support complex activities  processes Support rich interactions among autonomous parties  agents

Chapter 19Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Viewpoints on Services Traditionally, a capability that is provided and exploited, often but not always remotely Networking: bundle of bandwidth-type properties Telecom: features (caller ID, forwarding) Systems: operational functions (billing, storage); parceled up into operation-support systems Web or Grid: Web pages or Grid resources Wireless: Wireless access; messaging By contrast, we treat services as resembling real-life services or business partners

Chapter 110Service-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 (DestiCorp) A set of interfaces providing a standard means of interoperating between different software applications, running on a variety of platforms and frameworks (W3C) Our working definition: A service is functionality that can be engaged

Chapter 111Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Scope Includes wherever Internet and Web technologies are employed 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

Chapter 112Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Service Composition Vision Specify services independently of implementation Compose (to reuse) services in novel ways Go beyond the idea of a passive object Obviously desirable and challenging But is this what we want? Can or should implementations be hidden? What about organizational visibility? How to assess risk? How to handle exceptions?

Chapter 113Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Applications of Composable Services Portals Legacy system interoperation E-commerce Virtual enterprises Grid computing

Chapter 114Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Autonomy Independence of business partners (users and organizations) Political reasons Ownership of resources Control, especially of access privileges Payments Technical reasons Opacity of systems with respect to key features, e.g., precommit in distributed databases

Chapter 115Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Heterogeneity 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

Chapter 116Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Dynamism Independence of system administrators Needed because the parties change Architecture and implementation Behavior Interactions Make configurations dynamic to improve service quality and maintain flexibility

Chapter 117Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Locality: Avoiding Remote Dependencies Reduce sharing of data and metadata to reduce inconsistencies and anomalies Reduce hard-coding, which reflects out-of- band agreements among programmers Bind dynamically to components Use standardized formats to express data Express important knowledge as metadata Use standardized languages to express metadata Relax consistency constraints Minimize need for remote knowledge Correct rather than prevent violations of constraints: often feasible

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 FifthCollaborativeBusiness protocols Service engagements

Chapter 119Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Chapter 1 Summary Evolving perspectives on the Web Evolutions in IT architectures Open environments challenge some fundamental assumptions of computer science Autonomy Heterogeneity Dynamism Services, if understood correctly, can support IT in open environments