Service Oriented Architecture(SOA) Design Patterns

Service-oriented architecture (SOA) is an evolution of distributed computing based on the request/reply design paradigm for synchronous and asynchronous applications. An application's business logic or individual functions are modularized and presented as services for consumer/client applications. What's key to these services is their loosely coupled nature; i.e., the service interface is independent of the implementation. Application developers or system integrators can build applications by composing one or more services without knowing the services' underlying implementations. For example, a service can be implemented either in .Net or J2EE, and the application consuming the service can be on a different platform or language.

Why SOA?
The reality in IT enterprises is that infrastructure is heterogeneous across operating systems, applications, system software, and application infrastructure. Some existing applications are used to run current business processes, so starting from scratch to build new infrastructure isn't an option. Enterprises should quickly respond to business changes with agility; leverage existing investments in applications and application infrastructure to address newer business requirements; support new channels of interactions with customers, partners, and suppliers; and feature an architecture that supports organic business. SOA with its loosely coupled nature allows enterprises to plug in new services or upgrade existing services in a granular fashion to address the new business requirements, provides the option to make the services consumable across different channels, and exposes the existing enterprise and legacy applications as services, thereby safeguarding existing IT infrastructure investments.

Service-oriented architectures have the following key characteristics:

1. SOA services have self-describing interfaces in platform-independent XML documents. Web Services Description Language (WSDL) is the standard used to describe the services.

2. SOA services communicate with messages formally defined via XML Schema (also called
XSD). Communication among consumers and providers or services typically happens in heterogeneous environments, with little or no knowledge about the provider. Messages between services can be viewed as key business documents processed in an enterprise.

3. SOA services are maintained in the enterprise by a registry that acts as a directory listing. Applications can look up the services in the registry and invoke the service. Universal Description, Definition, and Integration (
UDDI) is the standard used for service registry.

4. Each SOA service has a quality of service (QoS) associated with it. Some of the key QoS elements are security requirements, such as authentication and authorization, reliable messaging, and policies regarding who can invoke services.

ref:

SOA Introduction

What is SOA -
http://www.javaworld.com/javaworld/jw-06-2005/jw-0613-soa.html

SOA Overview -
http://searchsoa.techtarget.com/generic/0,295582,sid26_gci1330269,00.html?offer=briefcase

SOA LifeCycle -
http://searchsoa.techtarget.com/guide/allInOne/0,296293,sid26_gci1262598,00.html?offer=briefcase

Principles of Service-Orientation -
http://searchsoa.techtarget.com/generic/0,295582,sid26_gci1172714,00.html?offer=briefcase

End-to-end testing for SOA and enterprise transactions -
http://searchsoa.techtarget.com/tip/0,289483,sid26_gci1357238_mem1,00.html

SOA patterns

SOA Patterns -
http://www.soapatterns.org/

SOA Design Patterns by Thomas Erl -
http://www.soapatterns.com/

SOA Design Patterns (by Arnon Rotem-Gal-Oz) -

http://www.rgoarchitects.com/Files/SoaPatterns.pdf

http://www.rgoarchitects.com/Files/SoaPatterns2.pdf

Best of Udi Dahan's Articles -
http://www.udidahan.com/first-time-here/

SOA Patterns: Implementing an SOA Using an Enterprise Service Bus(IBM Redbook) -
http://www.redbooks.ibm.com/redbooks/pdfs/sg246346.pdf

Patterns: SOA with an Enterprise Service Bus in WebSphere Application Server V6 -
http://www.redbooks.ibm.com/redbooks/pdfs/sg246494.pdf

SOA Anti-Patterns -
http://www.infoq.com/articles/SOA-anti-patterns

Service Facade -
http://searchsoa.techtarget.com/tip/0,289483,sid26_gci1346145_mem1,00.html

Non-Agnostic Context -
http://searchsoa.techtarget.com/tip/0,289483,sid26_gci1347582_mem1,00.html

Domain Inventory -
http://searchsoa.techtarget.com/tip/0,289483,sid26_gci1349152_mem1,00.html

Service Normalization -
http://searchsoa.techtarget.com/tip/0,289483,sid26_gci1350514,00.html

Service Decomposition -
http://searchsoa.techtarget.com/tip/0,289483,sid26_gci1352917_mem1,00.html

Miscellaneous

How SAML fits into your SOA security scheme -
http://searchsoa.techtarget.com/tip/0,289483,sid26_gci1337854_mem1,00.html

Tips for tracing enterprise transactions -
http://searchsoa.techtarget.com/tip/0,289483,sid26_gci1357445_mem1,00.html

Enterprise Architecture in the Agile age - Part 1, Styles of EA -
http://searchsoa.techtarget.com/tip/0,289483,sid26_gci1357017_mem1,00.html

SOA management vs SOA governance
http://searchsoa.techtarget.com/tip/0,289483,sid26_gci1335764,00.html

Business Process Execution Language (BPEL) Tutorial -
http://searchsoa.techtarget.com/generic/0,295582,sid26_gci1330911,00.html