Thursday, May 27, 2010

SOA Characteristic

SOA characteristics are defined below:

  • Service are discoverable and dynamically bound
  • Service provider use service registry to register service and Service consumer will use Service Registry to find out proper service and consume it. For an example, financial provider gives facility to validate credit card information and register their service with the system registry. They also provide more information like charges to validate credit card information. Service consumer will find all the services which helps to validate the credit card information and choose provider who gave service at lowest price.
  • Services are self contained and modular
  • Most important aspect of SOA is concept of modularity. A service supports a set of interfaces. These interfaces should be cohesive, meaning that they should all relate to each other in the context of a module.
  • Services stress interoperability
  • The ability of system is to be consumed by different platforms and languages to communicate with each other. Services dependencies are loose-coupled means loose-coupled services have a few well known dependencies.
  • Service have a network-addressable interface
  • The role of the network is central to the concept of SOA. A service must have a network-addressable interface. A consumer on a network must be able to invoke a service across the network. The network allows services to be reused by any consumer at any time. The ability for an application to assemble a set of reusable services on different machines is possible only if the services support a network interface.
  • Service have coarse-gained interfaces
  • The concept of granularity applies to services in two ways. First, it is applied to the scope of the domain the entire service implements. Second, it is applied to the scope of the domain that each method within the interface implements. The levels of granularity are relative to each other. For instance, if a service implements all the functions of a banking system, then we consider it coarsegrained. If it supports just credit-card validation, we consider it fine-grained. In addition, if a method for inquiring about a customer returns all customer information, including address, this method would be coarser-grained than a method that does not return the customer’s address.
  • Services are location transparent
  • Location transparency is a key characteristic of service-oriented architecture. Consumers of a service do not know a service’s location until they locate it in the registry. The lookup and dynamic binding to a service at runtime allows the service implementation to move from location to location without the client’s knowledge. The ability to move services improves service availability and performance. By employing a load balancer that forwards requests to multiple service instances without the service client’s knowledge, we can achieve greater availability and performance.
  • Services are composable
  • A service’s composability is related to its modular structure. Modular structure enables services to be assembled into applications the developer had no notion of when designing the service. Using preexisting, tested services greatly enhances a system’s quality and improves its return on investment because of the ease of reuse. A service may be composed in three ways: application composition, service federations, and service orchestration. An application is typically an assembly of services, components, and application logic that binds these functions together for a specific purpose. Service federations are collections of services managed together in a larger service domain. For example, a checking account service, savings account service, and customer service may be composed into a larger banking-account service. Service orchestration is the execution of a single transaction that impacts one or more services in an organization. It is sometimes called a business process. It consists of multiple steps, each of which is a service invocation. If any of the service invocations fails, the entire transaction should be rolled back to the state that existed before execution of the transaction.
  • Service-oriented architecture supports self-healing.
  • With the size and complexity of modern distributed applications, a system’s ability to recover from error is becoming more important. A self-healing system is one that has the ability to recover from errors without human intervention during execution.

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