IT Career Success

« Previous—Next »

Service-Oriented Architecture (SOA)

18 August 2006

A service-oriented architectue (SOA) is an application framework that takes everyday business applications and breaks them down into individual business functions and process, called services. An SOA let you build, deploy, and integrate these services independent of applications and the computing platforms on which they run.

Why SOA is so hot? SOA gives us a new way to architect loosely coupled activities and tasks, enterprise business services and reusable business components, and it assumes distributed sources of functionality and information. Also, SOA makes it possible to manage heterogeneous environments easily since SOA enforces standards to drive application content reuse and implements business service repository to discover, provision, and control heterogeneous resources.

Most importantly, SOA provides a new approach to build next generation applications. Within SOA, the next generation applications are model based, process driven, context aware, extensible/adaptable, and integrated through web services.

SOA infrastructure

To run and manage SOA applications, enterprises need an SOA infrastructure that is part of the SOA platform. An SOA infrastructure must support all the relevant standards and required runtime containers. A typical SOA infrastructure should have the following pieces.

1. WSDL, UDDI, and SOAP are the fundamental pieces of the SOA infrastructure. WSDL is used to describe the service; UDDI, to register and look up the services; and SOAP, as a transport layer to send messages between service consumer and service provider. While SOAP is the default mechanism for Web services, alternative technologies accomplish other types of bindings for a service. A consumer can search for a service in the UDDI registry, get the WSDL for the service that has the description, and invoke the service using SOAP.
2. WS-I Basic Profile, provided by the Web services Interoperability Organization, is turning into another core piece required for service testing and interoperability. Service providers can use the Basic Profile test suites to test a service’s interoperability across different platforms and technologies.
3. J2EE and .Net: Though the J2EE and .Net platforms are the dominant development platforms for SOA applications, SOA is not by any means limited to these platforms. Platforms such as J2EE not only provide the framework for developers to naturally participate in the SOA, but also, by their inherent nature, bring a mature and proven infrastructure for scalability, reliability, availability, and performance to the SOA world. Newer specifications such as Java API for XML Binding (JAXB), used for mapping XML documents to Java classes, Java API for XML Registry (JAXR), used for interacting with the UDDI registries in a standard manner, and Java API for XML-based Remote Procedure Call (XML-RPC), used for invoking remote services in J2EE 1.4 facilitate the development and deployment of Web services that are portable across standard J2EE containers, while simultaneously interoperating with services across other platforms such as .Net.
4. Quality of services: Existing mission-critical systems in enterprises address advanced requirements such as security, reliability, and transactions. As enterprises start adopting service architecture as a vehicle for developing and deploying applications, basic Web services specifications like WSDL, SOAP, and UDDI aren’t going to fulfill these advanced requirements. As mentioned previously, these requirements are also known as quality of services. Numerous specifications related to QoS are being worked out in standards bodies like the World Wide Web Consortium (W3C) and the Organization for the Advancement of Structured Information Standards (OASIS). Sections below discuss some of the QoS artifacts and related standards.
5. Security: The Web Services Security specification addresses message security. This specification focuses on credential exchange, message integrity, and message confidentiality. The attractive thing about this specification is it leverages existing security standards, such as Security Assertion Markup Language (SAML), and allows the usage of these standards to secure Web services messages. Web Services Security is an ongoing OASIS effort.
6. Reliability: On a typical SOA environment, several documents are exchanged between service consumers and service providers. Delivery of messages with characteristics like once-and-only-once delivery, at-most-once delivery, duplicate message elimination, guaranteed message delivery, and acknowledgment become important in mission-critical systems using service architecture. WS-Reliability and WS-ReliableMessaging are two standards that address the issues of reliable messaging. Both these standards are now part of OASIS.
7. Policy: ervice providers sometimes require service consumers to communicate with certain policies. As an example, a service provider may require a Kerberos security token for accessing the service. These requirements are defined as policy assertions. A policy may consist of multiple assertions. WS-Policy standardizes how policies are to be communicated between service consumers and service providers.
8. Orchestration: s enterprises embark on service architecture, services can be used to integrate silos of data, applications, and components. Integrating applications means that the process requirements, such as asynchronous communication, parallel processing, data transformation, and compensation, must be standardized. BPEL4WS or WSBPEL (Web Services Business Process Execution Language) is an OASIS specification that addresses service orchestration, where business processes are created using a set of discrete services. WSBPEL is now part of OASIS.
9. Management: As the number of services and business processes exposed as services grow in the enterprise, a management infrastructure that lets the system administrators manage the services running in a heterogeneous environment becomes important. Web Services for Distributed Management (WSDM) will specify that any service implemented according to WSDM will be manageable by a WSDM-compliant management solution.

No comments yet

Leave a Reply

Name (required)

Mail (will not be published) (required)

Website

Anti-spam word: (Required)*
To prove you're a person (not a spam script), type the security word shown in the picture.