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Introduction to SOA and Web Services

B. Ramamurthy

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Introduction

A Service-Oriented Architecture (SOA) is a design model for linking computational resources, data and applications to perform services and deliver results to service consumers.

Web Service (WS) standard provides a platform-independent method for messaging-based interaction of applications.

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Topics for Discussion

How did we get here? State of computing and business

Effect of scientific advances on industries, information technology (IT), computing research, environment, society,… ?

Role of SOA and services SOA principles (Ch.1) Evolution of the service concept (Ch.2)

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Evolution

Industrial Automation Just-in-time Advances in supply chain …

Business Remote operations Heterogeneity Scale Integration (application, data) E-commerce …

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Evolution (contd.)

Information technology Internet World-wide web Grid Mobile and wireless Devices Software, platforms Search engines Tremendous advances

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Evolution (contd.)

Computing research Programming languages RISC vs. CISC architectures Memory capacity Computing power Simple programObject Component…

Environment Accessibility Globalization (outsourcing, markets) ...

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Evolution (contd.)

Society IT users not exclusive to Computer Science Digital media ipod, iphone, idog,.. Youtube, myspace, social networking Blogs,wikies, podcasts …

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Evolutionary Theory

Industry

Business

Research

IT

Environment

Society

Pieces of the pie..

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Evolutionary Theory

Industry

Business

Research

IT

Environment

Society

SOA can align the pieces!!?

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Missing pieces?

Question (Homework assignment)

Are there any categories that I did not consider in the pie? Ex: government policies?

What should be the appropriate weight of each category? For example, consider the heavy weight given to IT in the picture on the right.

Evolutionary Theory

Industry

Business

Research

IT

Environment

Society

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SOA Principles Loosely coupled (service provider and service consumer are

loosely coupled: why?) Large scale: complex system with high level of heterogeneity

and redundancies. Decoupling of functionality and technology Service contract and agreements Discoverability On demand composability of services: composite services

concept Agility: respond to changes quickly Statelessness Inherent interoperability Standards Simplicity Reusability

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Typical Enterprise Complex heterogeneous system:

Examples: CRM (Customer relationship management) system, insurance claims processing system

Stakeholders Highly heterogeneous teams Different political environments CEO, IT projects, customers, operations

Different applications and middleware Content and data with varying lifetime Potentially large number of end users

Applications have to be rolled out to a large number of PCs, say,10000

Major changes and ongoing incremental optimization need to be handled efficiently in an agile manner.

An SOA addresses these needs.

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Evolution of the service concept

A service is a meaningful activity that a computer program performs on request of another computer program.

Technical definition: A service a remotely accessible, self-contained application module.

From IBM,

Service

Component

Object/Class

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Class, Component and Service

Class is a core concept is object-oriented architectures. An object is instantiated form a class. Focus on client side, single address space programs.

Then came the component/container concept to improve scalability and deployability. Ex: EJBs. Focus on server side business objects and separation

of resources from code. Service came into use when publishing,

discoverability, on-demand operation among interacting enterprise became necessity. Focus of enterprise level activities, contracts,

negotiations, reservations, audits, etc.

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Object-oriented programming

Object-oriented programming Encapsulation of data and function in a class,

instances of a class is called an object Objects communicate through messages (invoking

methods) Class represents a type from which another type can

be derived resulting inheritance hierarchy. Problem: level of abstraction and granularity exposed

is fine to enable reuse. Data and functions are tightly coupled. Important contribution SOA: concept of interface

Service-orientation assumes that data and functionality are separated.

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Distributed Computing

Important challenge is find abstractions for both remoteness and actual service task at the same time.

Simple interfaces such a telnet, rlogin emerged for remoting.

Distributed Computing Environment (DCE), Common Object Request Broker Architecture (CORBA) emerged as middleware. “interoperability” was an important goal. IDL Interface definition language came into existence.. IDL is a predecessor of WSDL Heavy weight infrastructure resulted in discovery of the

light weight XML solution. XML, SOAP over HTTP, WS emerged.

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Business Computing

File systems to main frames Emergence of new paradigms such as Enterprise

Resource Planning (ERP) and Supply Chain Management (SCM) placed complex requirements on the computing machines and applications.

This was followed by huge compute (IT) demands for Enterprise Application Integration (EAI) and Enterprise Data Integration (EDI).

An appealing characteristic of SOA is that it aligns these business entities by directly mapping them to services, thus enabling an enterprise integration on the business level, not on the technical level.