Service Oriented Architecture - Notes

Service Oriented Architecture (SOA) Service-oriented architecture (SOA) is an approach to loosely coupled, protocol independent, standards-based distributed computing where software resources available on the network are considered as Services. SOA is believed to become the future enterprise technology solution that promises the agility and flexibility the business users have been looking for by leveraging the integration process through composition of the services spanning multiple enterprises. Characteristics • The software components in a SOA are services based on standard protocols. • Services in SOA have minimum amount of interdependencies. • Communication infrastructure used within an SOA should be designed to be independent of the underlying protocol layer. • Offers coarse-grained business services, as opposed to fine-grained softwareoriented function calls. • Uses service granularity to provide effective composition, encapsulation and management of services. Service Granularity Service granularity refers to the scope of functionality a service exposes. Fine-grained services provide a small amount of business-process usefulness, such as basic data access. Coarse-grained services are constructed from fine-grained services that are intelligently structured to meet specific business needs. Service Composition

Service Management There are three levels of service management • Management of the services and their interfaces

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• •

Management of the underlying system Management of the interaction between the services and the underlying system

SOA Meta-Model SOA is a form of enterprise architecture and can be represented using models. SOA meta-model is a model that contains the following three models.

Differences: SOA vs. Existing Model Driven Architecture (MDA) SOA is an alternative model to the more traditionally tightly-coupled object-oriented models like Common Object Request Broker Architecture (CORBA) and Distributed Component Object Model (DCOM). In SOA individual services can be build with objectoriented designs but the overall design of SOA is service-oriented. SOA today differs in the usage of a more generic standard-based interface language XML (eXtensible Markup Language) used in Web Services Definition Language (WSDL) compared to the older Interface Definition Language (IDL) found in CORBA. SOA is based on the concept of using services that can communicate through standard protocols like SOAP allowing a more loosely coupled architecture. In older models objects were more tightly coupled due to the usage of vendor specific communication standards. IBM’s MQSeries is yet another message-oriented middleware system but it lacks the organized workflow definition required for the services to interoperate. SOA supports the composition of coarse-grained services from fine-grained services to provide a business solution in an easily deployable and usable manner. For interoperability of services spanning multiple enterprises, SOA should provide service level agreements and operational policies. Web Services and SOA Web Services are an open standards-based way of creating and offering SOAs. Web Services are able to exchange structured documents that contain different amounts of information, as well as information about that information, known as metadata. In other words, Web Services can be coarse grained. Such coarse granularity is one of the most important features of SOAs. SOA Implementation Framework

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Service-Oriented Architecture Implementation Framework (SOAIF) provides the run-time deployment infrastructure for SOA across the network by incorporating all the software required to develop, deploy, secure, manage, and extend service-oriented processes and solutions. SOA Implementation Framework

Enterprise Service Bus (ESB) ESB is the backbone of SOA that acts as a message broker providing a message queuing system using industry standard specifications for messaging such as SOAP, or JMS (Java Message Service). Expert Sally Hudson, an IDC analyst, describes the Enterprise Service Bus as an open standards-based messaging means designed to provide interoperability between largergrained applications and other components via simple standard adapters and interfaces. ESB Architecture

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ERP Transformation (XSLT)

.NET JCA

Web Services

SOAP/ HTTP

SOAP/ HTTP

Reliable Asynchronous Secure Messaging

Connection Layer

Communication Layer

SOAP/HTTP JMS C/C++ Legacy Application

J2EE

Connection Layer

Re-architecture to SOA Encapsulate software components, applications and underlying systems with Web Services interfaces Compose (virtualizing) these fine-grained functional Web Services into coarse-grained business services Benefits • Provides location independence: Services need not be associated with a particular system on a particular network • Protocol-independent communication framework renders code reusability • Offers better adaptability and faster response rate to changing business requirements • Allows easier application development, run-time deployment and better service management • Loosely coupled system architecture allows easy integration by composition of applications, processes, or more complex services from other less complex services • Provides authentication and authorization of Service consumers, and all security functionality via Services interfaces rather than tightly-coupled mechanisms • Allows service consumers (ex. Web Services) to find and connect to available Services dynamically Why Not SOA • For a stable or homogeneous enterprise IT environment, SOA may not be important or cost effective to implement. • If an organization is not offering software functionality as services to external parties or not using external services, which require flexibility and standardbased accessibility, SOA may not be useful. • SOA is not desirable in case of real time requirements because SOA relies on loosely coupled asynchronous communication. Self Management Using SOA

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Web Services now lack workflow support, asynchronous communication and standards for efficient interoperability, dynamic integration and deployment which can be provided using SOA. SOA leverages the management functionality of the services in its implementation framework which can be effectively used to provide better self-management for the services within the infrastructure.

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