computing with services cs 696 – services computing fall 2008
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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. Highlights of this Chapter. (1) Visions for the Web (2) Open Environments (3) Services Introduced - PowerPoint PPT PresentationTRANSCRIPT
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Computing with ServicesCS 696 – Services Computing
Fall 2008
Chapter 1, Service-Oriented Computing: Semantics,
Processes, Agents – Munindar P. Singh and Michael N. Huhns, Wiley, 2005
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Highlights of this Chapter
(1) Visions for the Web(2) Open Environments(3) Services Introduced(4) The Evolving Web(5) Standards Bodies
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(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
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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
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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
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Brief History of Information Technology
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System Architectures: Centralized
Mainframe
Terminal3270
Terminal
Terminal
Terminal
Terminal
TerminalTerminal
Terminal
Terminal
Terminal
Terminal
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System Architectures: Client-Server
E-MailServer
WebServer
DatabaseServer
PCClient
PCClient PC
Client
WorkstationClient
Master-Slave
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System Architectures: Peer-to-Peer
E-MailSystem
WebSystem
DatabaseSystem
Application
ApplicationApplication
Application
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System Architectures: Cooperative
E-MailSystem
WebSystem
DatabaseSystem
Application
ApplicationApplication
Application
(Mediators, Proxies, Aides, Wrappers)
Agent
Agent
Agent
Agent
Agent
Agent
Agent
Agent
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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
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(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
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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
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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
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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
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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
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(3) Services IntroducedHistorical 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
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(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
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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
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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
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(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)
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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
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Standards for Web Services
BPEL4WSOWL-S Service
Model
ebXMLCPA
Process and workfloworchestrations
QoS: Servicedescriptions and bindings
Contracts andagreements
XLANG
WSCL
WSDLebXML
CPP
ebXMLBPSS
XML, DTD, and XML Schema
HTTP, FTP, SMTP, SIP, etc.
SOAPebXML
messaging
OWL
UDDIebXML
Registries
WSCLWSCI
WS-Coordination
WS-AtomicTransaction and WS-BusinessActivity
OWL-S ServiceGrounding
OWL-S ServiceProfile
BTP
BPML
Discovery
Messaging
Transport
QoS: Conversations
QoS: Choreography
QoS: Transactions
Encoding
WS-Policy
WS-Security
WS-ReliableMessaging
PSL
RDF
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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
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eXtensible Markup Language (XML)
Simple Object Access Protocol (SOAP)
Web Services Description Language (WSDL)
Directory Services Universal Description, Discovery,
and Integration (UDDI)
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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