• Interfaces are used to deliver descriptive messages defined through extensible schemas (i.e. a schema defines the vocabulary and structure of messages). An extensible schema allows new versions of services to be introduced without breaking existing services. Messages are not intended to describe the system behavior.

The above example illustrates that interfaces play an impor tant roll in any system. For a distributed application system interfacing is less error-prone and comparably costlier. It is quite difficult to implement without knowing the system behavior across different platforms and languages. It is better to reuse the few generic interfaces for all the applications. We can send any kind of messages over the interfaces just Service Oriented Architectur by following the few kinds of rules like:

• Since the service provider is responsible to solve any kind of problem therefore the message must be descriptive rather than instructive. It’s just like going to a restaurant and place an order without bothering the cooking steps.

• Service provider will not be able to understand if the message is not properly formatted by using the standard rules. Providing the limitations to a message is the basic need to make the communication most effective. It is easier to understand as long as the message is restricted, although it is much expensive to reduce extensibility.

Broadly SOA can be classified into two terms: Services and Connections

Services: A service is a function or some processing logic or business processing that is well-defined, self-contained, and does not depend on the context or state of other services. Example of Services are Loan Processing Services, which can be self-contained unit for process the Loan Applications. Other example may be Weather Services, which can be used to get the weather information. Any application on the network can use the service of the Weather Service to get the weather information.

Connections: Connections means the link connecting these self-contained distributed services with each other, it enable client to Services communications. In case of Web services SOAP over HTTP is used to communicate the between services.
The following figure is a simple illustration of the serviceoriented architecture. It shows how a service consumer sends a service request to a service provider. After accepting the request, service provider send a message to the service consumer. In this case a service provider can also be a service consumer.


Different Technologies Used:

SOA is much different from point-to-point architectures. SOA comprise of loosely coupled, highly interoperable application services. These services can be developed with different development technologies (such as Java, .NET, C++, PERL, PHP), the software components become reusable i.e. the same C# (C Sharp) service may be used by a Java application (and/or any other programming language).

SOA Terminologies

Term Definition
Service (Ideally) a self-contained, stateless business func
tion which accepts one or more requests
and returns one or more responses through a well-defined, standard interface. Services can also perform discrete units of work such as editing and processing a transaction. Services should not depend on the state of
other functions or processes. The echnol
ogy used to provide the service, such as a programming language, does not form part of this definition.
Orchestration Sequencing services and providing addi
tional logic to process data. Does not
include data presentation.
Stateless Not depending on any pre-existing condi tion. In a SOA, services should not depend on the condition of any other service. They receive all information needed to provide a
response from the request. Given the
statelessness of services, service consum
ers can sequence (orchestrate) them into numerous flows (sometimes referred to as pipelines) to perform application logic.
Provider The function which performs a service in response to a request from a consumer.
Consumer The function which consumes the result of a service supplied by a provider.
Discovery Service oriented architecture relies on the ability to identify services and their capabili ties. Therefore, a SOA depends on a directory which describes the services available in its domain.
Binding The relationship between a service provider and consumer is dynamic; it is established at runtime by a binding mechanism.
August 2007 | Java Jazz Up |29
Pages: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30,
31, 32, 33, 34, 35, 36, 37, 38, 39, 40           Download PDF