Introduction To Web Services And Soa

Seminar: Distributed Software-Systems

Introduction to Web Services Christoph Weyer

TU Hamburg-Harburg 19th April 2004

Introduction to Web Services Outline of the Presentation 1. Requirements for e-Business 2. Service Oriented Architecture 3. Web Services 4. Architecture and Standards 5. Summary

Christoph Weyer: Introduction to Web Services

TU Hamburg-Harburg, 19th April 2004

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Requirements for e-Business

• information exchange and information integration • paradigm shift towards machine-to-machine interactions • shift to peer-to-peer architecture • abstraction beyond object-oriented technology • integration on service semantics (business process-based) • loosely coupled interactions • business partner interactions are moving towards dynamic agreements

• just-in-time integration Christoph Weyer: Introduction to Web Services

TU Hamburg-Harburg, 19th April 2004

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Service Oriented Architecture (SOA) Service Broker

Publish

Find

Service Contract ... ...

Service Provider

Service Consumer Bind see [Hégaret 2003] Christoph Weyer: Introduction to Web Services

TU Hamburg-Harburg, 19th April 2004

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Architectural Constraints of SOA

• small set of simple and ubiquitous interfaces to all participating entities

• interfaces should be universally available • messages must be descriptive, rather than instructive • no system behaviour is prescribed by messages • messages constrained by an extensible schema • schema limits the vocabulary and structure of messages • extensible schema allows new versions of services to be introduced without breaking existing services

Christoph Weyer: Introduction to Web Services

TU Hamburg-Harburg, 19th April 2004

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Web Services SOA is the basic idea behind Web Services! Used XML-based Technologies • SOAP (Simple Object Access Protocol) defines an envelope for Web Services communication and provides a serialisation format for transmitting XML documents

• WSDL (Web Services Description Language) defines Web Services interfaces, data and message types, interaction patterns, and protocol mappings

• UDDI (Universal Description, Discovery, and Integration) Web Services registry and discovery mechanism, is used for storing and categorising interfaces Christoph Weyer: Introduction to Web Services

TU Hamburg-Harburg, 19th April 2004

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Web Services Model Service Broker

UDDI

Publish

Find

Service Contract ... L ... SD

Service Consumer

SOAP Bind

W

Service Provider

Web Service

see [Hégaret 2003] Christoph Weyer: Introduction to Web Services

TU Hamburg-Harburg, 19th April 2004

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Advantages of Web Services • Interoperability . any Web Service can interact with any other Web Service . platform independent and based on open standards

• Ubiquity . based on HTTP and XML . Web technologies are widely spread

• Low barrier to Entry . concepts are easy and simple . existing knowledge of XML-based technologies

• Industry Support . all major vendors are supporting SOAP and Web Services . already integrated in many applications (e.g. .NET, Office) Christoph Weyer: Introduction to Web Services

TU Hamburg-Harburg, 19th April 2004

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Web Services Everywhere? (I) "The Computer can search for You!" (Google)

• Google offers a Web Service • auto-monitoring the web for new information on a subject

• glean market research insights and trends over time

• use your own UI for searching the web http://www.google.com/apis/

Christoph Weyer: Introduction to Web Services

TU Hamburg-Harburg, 19th April 2004

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Web Services Everywhere? (II) • Web Service that helps photographyrelated businesses enhance their services

• Common Picture eXchange environment (CPXe)

• combine services from different vendors and retailers

• PSN members . Kodak . Agfa . ...

http://www.pictureservices.org/ Christoph Weyer: Introduction to Web Services

TU Hamburg-Harburg, 19th April 2004

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Open Issues • Security . basic security with HTTP over SSL . other issues are addressed by WS-Security

• Transaction . traditional transaction architecture for closed environments . is addressed by WS-Coordination and WS-Transaction

• Reliability of Communication deals with reliable message deliver ⇒ WS-ReliableMessaging

• Scalability . performance issue → overhead through XML & SOAP . orchestration and aggregation of lower-level Web Services ⇒ BPEL4WS and WSCDL

• Manageability and Testing Christoph Weyer: Introduction to Web Services

TU Hamburg-Harburg, 19th April 2004

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Web Services Protocol Architecture

Security

BPEL4WS

Service Composition

Reliable Messaging

Composable Service Assurances

Transactions

WSDL, UDDI, Policy, MetadataExchange

Description

SOAP (Logical Messaging) Messaging XML (Encoding) Transport

HTTP, HTTPS, SMTP see [Ferguson 2003] Christoph Weyer: Introduction to Web Services

TU Hamburg-Harburg, 19th April 2004

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Summary Challenges for e-Business • service orientation • loosely coupled machine-to-machine interactions Standards are evolving • flaws in Web Services architecture • ensure interoperability Are Web Services a Revolution? • new paradigm for distributed architectures • misapplication of Web Services • still simple? Christoph Weyer: Introduction to Web Services

TU Hamburg-Harburg, 19th April 2004

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Questions ???

Christoph Weyer: Introduction to Web Services

TU Hamburg-Harburg, 19th April 2004

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References [Ferguson 2003]

Donald F. Ferguson, et. al.: Secure, Reliable, Transacted Web Services: Architecture and Composition, MSDN Library, 2003. http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnwebsrv/html/wsoverview.asp

[Glass 2000]

Graham Glass: The Web Services (R)evolution - Applying Web Services to Applications, IBM developerWorks, 2000. http://www-4.ibm.com/software/developer/library/ws-peer1.html

[Graham 2001]

Steve Graham, et. al.: Building Web Services with Java: Making Sense of XML, SOAP, WSDL, and UDDI, Sams Publishing, 2001.

[Hégaret 2003]

Philippe Le Hégaret: Introduction to Web Services, 2003. http://www.w3.org/2003/Talks/0317-ws-intro/

[Kreger 2001]

Heather Kreger: Web Services Conceptual Architecture (WSCA 1.0), IBM Software Group, 2001. http://www.ibm.com/software/solutions/webservices/pdf/WSCA.pdf

[Newcomer 2002] Eric Newcomer: Understanding Web Services: XML, WSDL, SOAP, and UDDI, Addison Wesley Professional, Independent Technology Guides, 2002. [Ogbuji 2002]

Uche Ogbuji: The Past, Present and Future of Web Services, Part 1, 2002. http://www.webservices.org/index.php/article/articleprint/663/-1/24/

[Tidwell 2000]

Doug Tidwell: Web Services: The Web’s next revolution, IBM developerWorks, 2000. http://www-106.ibm.com/developerworks/edu/ws-dw-wsbasics-i.html

[W3C 2004]

W3C: Web Services Glossary, W3C Working Group Note, 2004. http://www.w3.org/TR/2004/NOTE-ws-gloss-20040211/

Christoph Weyer: Introduction to Web Services

TU Hamburg-Harburg, 19th April 2004

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