1. Introduction to SOA and Web Services
B. Ramamurthy
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2. 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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3. 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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4. Evolution Industrial Business Automation Just-in-time
Advances in supply chain …
Business
Remote operations
Heterogeneity
Scale
Integration (application, data)
E-commerce
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5. Evolution (contd.) Information technology Internet World-wide web Grid
Mobile and wireless
Devices
Software, platforms
Search engines
Tremendous advances
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6. Evolution (contd.) Computing research Environment
Programming languages
RISC vs. CISC architectures
Memory capacity
Computing power
Simple programObject Component…
Environment
Accessibility
Globalization (outsourcing, markets)
...
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7. 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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8. Pieces of the pie..
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9. SOA can align the pieces!!?
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10. 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.
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11. 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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12. 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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13. 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,
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14. 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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15. 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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16. 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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17. 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.
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