What is Service Oriented Architecture ? CS409 Application Services Even Semester 2007.

What is Service Oriented Architecture ?

CS409 Application ServicesEven Semester 2007

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Definition

• Service: unit of logic to exist autonomously but not isolated.

• Architecture: standardized structure of a baseline system.

• SOA:– A form of technology architecture that adheres

to the principles of service-orientation.

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Service-Orientation Principles

• Loose coupling– Minimizes dependencies, retain awareness of

each other.

• Contract– Adhere to a communication agreement.

• Autonomy– Encapsulate logic and have control over it.

• Abstraction– Hide logic from outside world, only explain the

communication agreement.

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Service-Orientation Principles (2)

• Reusability– Logic is divided with the intention of reuse.

• Composability– Collections of services are able to form

composite services.

• Stateless– Minimize retain specific information.

• Discoverability– Descriptive so can be found and assessed via

discovery mechanism.

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Web Service

• A pure, web-based, distributed technology that leverage the concept of SOA.

• Transported over the internet communication framework.

• Designed to bridge disparities existed between information systems.

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Why Web Service?

• INTEGRATION issue: – How to easily manage the heterogeneity of

enterprise systems?– How to deliver next generation of application

while leveraging existing IT investment?

• Available integration technology solutions are proprietary and not interoperable.– Tibco, Bowstreet, LonMaker, etc

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Why Web Service? (2)

• Necessity for integration and interoperability of enterprise systems through common delivery channel (the web).

• Applications need standard ways to access middle-tier and back-end of other applications (reuse existing assets).

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Web Service Timeline

• Late 60s: SGML (Standard Generalized Markup Language).

• Late 90s: – XML (Extensible Markup Language), – XSD (XML Schema Definition Language), – XSLT (XML Schema Transformation Language).

• 2000: SOAP• 2001: WSDL• 2002: UDDI

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Web Service Timeline (2)

• It is not something really new.– Middleware concept, e.g. DCOM, CORBA

• Similar to RPC over HTTP protocol.

• The ‘new’ core of web service is XML:– Makes it easier to share data among different

applications.– Makes it easier to define the standard for

interoperability.

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Standard Organizations

• The World Wide Web Consortium (W3C)– HTML, XML, XSD, XSLT.

• Organization for the Advancement of Structured Information Standards (OASIS)– SGML, WS-BPEL, ebXML, UDDI, SAML, XACML.

• The Web Services Interoperability Organization (WS-I)– Recommendations to collectively use available

standards: Basic Profile, Basic Security Profile.

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Architecture

Four layers protocol stack:

1. Service description: describing public interface to clientse.g. WSDL, WSFL, etc.

2. Service discovery: providing easy publish/find functionality by clientse.g. UDDI, USML, ebXML Registry, etc.

3. Service transport: transporting messages between providers and clientse.g. FTP, SMTP, HTTP, BEEP, etc.

4. Messaging: encoding messages to be recognized and utilized e.g. XML-RPC, SOAP, SOAP-DSIG, etc.

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Architecture (2)

• All technologies are XML-based standard to ensure interoperability and portability.

• Platform independent, enable diverse applications to communicate with one another.

• Standards are defined by organizations (W3C, OASIS, WS-I).

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1. Service provider registers service in a public registry directory.

2. Consumer uses the directory to find service that matched.

3. Registry provides consumer with contract and endpoint address.

4. Consumer requests service provider.

5. Service provider responds to the consumer.

Fig 1. Find-Bind-Execute Paradigm

How Web Service Works

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How Web Service Works (2)

Fig 2. XML Message Flows in Web Service

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How Web Service Works (3)

Fig 3. Java client calling J2EE Web Service

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Web Service Benefits

• Improved integration– Vendor-neutral, intrinsic interoperability.

• Inherent reuse– Lower cost and effort of development.

• Streamlined architecture– Composability, reduce processing effort.

• Leveraging investment.– Reuse existing legacy system.

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Web Service Benefits (2)

• Standardized data representation– XML representation, reduce complexity.

• Focused investment on infrastructure– Common communication framework.

• “Best-of-breed” alternatives– Vendor neutral, free from proprietary

technology.

• Organizational agility– Abstracting business logic into service layers.

Thank You

Doddy [email protected]

[email protected]