Service Oriented Architecture SOA And Web Services

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Service Oriented Architecture (SOA)And Web
Services

• By
• Ahmed Chaudhary

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Presentation overview

• Introduction to SOA
• Through Examples and Metaphors
• Introduction to Web Services
• Brief overview of XML Technologies
• Comparison of SOA and services with other
  paradigms
  
• Benefits and limitations of SOA

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A business trip in the not so distant future
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Information Technology used in this trip

• Keeping track of all the customer contacts in an
  online repository
  
• Obtaining Company Contact Information from an
  External Service
  
• Online Calendar Services
• Getting Updates on Clients to Be Visited While on
  the Road
  
• Travel Agency Service
• Car Rental Service
• Airlines and Hotel
• Services as Commodities

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Another Example
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SOA Explained

• A service-oriented architecture is essentially a
  collection of services.
  
• These services communicate with each other
• Some mechanism of connecting services to each
  other is needed. Those connections are Web
  Services.

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What is a service ?

• A function that is well-defined
• Self-contained
• Does not depend on the context or state of other
  services.

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The Mail-Order Business

• A Mail-Order Business is Asynchronous
• Work Requests Arrive in Bags of Mail
• Product Arrives in Shipments
• Each Message (Order) Is a Transaction
• Goods Are Prepared and Packed
• Payment Is Processed
• Stuff is Shipped
• Standards and Interchangeability Required
• Both Goods and Forms
• Mail-Order Is a Service-Oriented Architecture!
• Well defined functions
• Self-contained
• Independent

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How Services Work
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Web Services

• Web services are the mechanism for connecting
  services programmatically and are based on
  standards.
  
• Other existing connection mechanisms
• CORBA
• DCOM
• EDI etc.

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How Web Services Work
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More on Web Services

• Web services can be published, located, and
  invoked across the Web.
  
• The standards required to do so are
• Simple Object Access Protocol (SOAP), also known
  as service-oriented architecture protocol, an
  XML-based RPC and messaging protocol
  
• Web Service Description Language (WSDL), a
  descriptive interface and protocol binding
  language
  
• Universal Description, Discovery, and Integration
  (UDDI), a registry mechanism that can be used to
  look up Web service descriptions
  

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Some points about Web Services

• Services arent tied to user interfaces.
• Services can be implemented in any language,
  COBOL, Java, etc., but all services must support
  the same invocation/communication protocols (for
  example XML/SOAP)

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Introduction to XML and related Technologies
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What is XML?

• XML stands for EXtensible Markup Language
• XML is a markup language much like HTML
• XML was designed to describe data
• XML tags are not predefined. You must define your
  own tags

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An Example
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What is an XML Schema?

• The purpose of an XML Schema is to define the
  building blocks of an XML document
  
• defines elements that can appear in a document
• defines which elements are child elements
• defines the order of elements
• defines the number of child elements
• defines data types for elements and attributes

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What is SOAP?
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What is WSDL?

• WSDL stands for Web Services Description
  Language.
  
• WSDL is a document written in XML.
• The document describes a Web service. It
  specifies the location of the service and the
  operations (or methods) the service exposes.

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Comparisons of SOA
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SOA vs CORBA DCOM
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SOA vs. Enterprise Integration Architecture (EIA)

• EIA is being reactive
• SOA is being proactive

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Services vs. Components

• A service is a coarse-grained processing and maps
  to a business function
  
• A component typically maps to business entities
  and the business rules
  

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An example component model
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Revisiting the Business Trip
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Why do we need SOA?

• There's little "green field" anymore
• New stuff needs existing stuff
• Existing stuff needs new stuff
• Heterogeneous Systems
• No single OS-family / HW-platform
• Deal with "Big Bang" Effect
• Everything keeps drifting farther away from
  everything else
  
• Access/Manipulate data from anywhere

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SOA Benefits

• Leverage existing assets.
• Easier to integrate and manage complexity.
• More responsive and faster time-to-market.
• Reduce cost and increase reuse.
• Be ready for what lies ahead.

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SOA Limitations

• SOA requires an environmental framework
• Pending security issues
• Handling Transactions

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Summary

• SOA is an architectural style that encourages the
  creation of loosely coupled business services
  Loosely coupled services that are interoperable
  and technology-agnostic enable business
  flexibility
• An SOA solution consists of a composite set of
  business services that realize an end-to-end
  business process
  
• Each service provides an interface-based service
  description to support flexible and dynamically
  re-configurable processes

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Q A