Service Oriented Architecture

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Service Oriented Architecture
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What is a Web Service

• A Web service is a software system designed to
  support interoperable machine-to-machine
  interaction over a network. It has an interface
  described in a machine processable format
  (specifically WSDL). Other systems interact with
  the Web service in a manner prescribed by its
  description using SOAP messages, typically
  conveyed using HTTP with an XML serialization in
  conjunction with other Web-related standards
  W3C

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Web Services

• Need not exist on the World Wide Web
• Can live anywhere on the network, Inter- or
  intranet
• Little to do with browser-centric, HTML-focused
  WWW
• Web service implementation and deployment are
  irrelevant to the invoking program
• Minimal shared understanding between cooperating
  components

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Business Perspective

• Web Services is about integrating application
  functionality within an organization or
  integrating applications between business
  partners
• A Web Service is a business process or step
  within a business process that is made available
  over a network to internal or external business
  partners to achieve a business goal

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Technical Perspective

• Web Services are collections of operations that
  are accessible over a network and described by a
  service description
• Web Services are loosely coupled. The only
  specification between a provider and a consumer
  service is an interface

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Service-Oriented Architectures

• In SOA, all software components (those visible
  for consumption) are modeled as services.
  Business processes are built to be consumed as
  services over a network
• The design focus is on the interface
• Services are small, well-defined, and
  multi-purpose
• Services can be combined or orchestrated to
  produce different results

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SOA

• Applications are integrated at the interface
  (contract) level, not at the implementation level
• Applications work with any implementation of a
  contract
• Different service providers can be dynamically
  chosen based on policies

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SOA Three Roles

• Service Provider Creates a service description,
  deploys the service over the network, publishes
  the service description in a service registry
  (Server)
• Service Requestor Finds a service published in
  a registry, uses the service description to
  invoke the service (Client)
• Service Registry Advertises web service
  descriptions published by service providers

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SOA Three Roles
Service Registry
Publish
Find
Service Requestor
Service Provider
Bind
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Why is SOA Important?

• Promises to be easier to integrate business
  processes and respond rapidly to changes in the
  business environment
• Software integration by connecting diverse
  components
• IT and Business concepts are closer together.
  This encourages good modeling of business
  processes

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SOA vs Web Services

• These are two distinct terms
• SOA is an architectural concept that emphasizes
  building systems based on a loosely coupled set
  of components that can be dynamically composed
• Web Services is one approach to building an SOA.
  Web services provides a standard for a particular
  set of XML-based technologies

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E-Business Trends

• Finding resources automatically without human
  intervention
• Moving from rigid, brittle systems to more
  flexible architectures
• Moving from static agreements to dynamic ones for
  business partner interactions
• Moving from proprietary technology-based
  integration to business process-based integration
  using open standards

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Why Has this Happened?

• TCP/IP used as an open platform for networking
• WWW, HTML, HTTP provided an open portable user
  interface
• Java provides open portable programming
• XML allows portable data exchange
• Remote Procedure Call (RPC) interfaces replaced
  with document-centric models

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When to Use WS?

• Parts of the solution are distributed
• Components built by different organizations
• The components exist on heterogeneous platforms
• The business process should be automated. If
  human intervention is required, use browsers,
  JSPs, servlets

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When to Use WS?

• The business process and components change with
  some frequency
• The business process is policy driven
• The business process isnt core and might be
  outsourced
• Data needs to be available to many requestors

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WS Interoperability Stack
Compositional
BPEL4WS, WS-Notification
Quality of Experience
WS-Security, WS-ReliableMessaging,
WS-Transactions, WS-ResourceLifetime
WSDL, WS-Policy, UDDI, WS-ResouceProperties
Description
XML, SOAP, WS-Addressing
Messaging
HTTP, HTTPS, SMTP, Etc.
Transports
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