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

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

Chapter 1 2Service-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 1 3Service-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

Chapter 1 4Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and

Michael Huhns

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

Chapter 1 5Service-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

Chapter 1 6Service-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.

Chapter 1 7Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and

Michael Huhns

Brief History of Information Technology

Chapter 1 8Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and

Michael Huhns

System Architectures: Centralized

Mainframe

Terminal3270

Terminal

Terminal

Terminal

Terminal

TerminalTerminal

Terminal

Terminal

Terminal

Terminal

Chapter 1 9Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and

Michael Huhns

System Architectures: Client-Server

E-MailServer

WebServer

DatabaseServer

PCClient

PCClient PC

Client

WorkstationClient

Master-Slave

Chapter 1 10Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and

Michael Huhns

System Architectures: Peer-to-Peer

E-MailSystem

WebSystem

DatabaseSystem

Application

ApplicationApplication

Application

Chapter 1 11Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and

Michael Huhns

System Architectures: Cooperative

E-MailSystem

WebSystem

DatabaseSystem

Application

ApplicationApplication

Application

(Mediators, Proxies, Aides, Wrappers)

Agent

Agent

Agent

Agent

Agent

Agent

Agent

Agent

Chapter 1 12Service-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 InternetWhen we talk about Internet computing or Web

services, we consider all of the above as possible environments

Chapter 1 13Service-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

Chapter 1 14Service-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

Chapter 1 15Service-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

systemsBest not to assume homogeneity

Chapter 1 16Service-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

Chapter 1 17Service-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

Chapter 1 18Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and

Michael Huhns

Historical View of Services over the Web

Generation

Scope Technology

Example

First All Browser Any HTML page

Second Programmatic

Screen scraper

Systematicallygenerated HTMLcontent

Third Standardized

Web services

Formally described service

Fourth Semantic Semantic Web services

Semantically described service

Chapter 1 19Service-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

Chapter 1 20Service-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

Chapter 1 21Service-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