What is Service Oriented Architecture - Cost

Service-Oriented Architecture (SOA) is great isn't it? Chaos becomes order. Services are available for everybody to reuse. Costs are lowered. The business is truly agile. Shareholders are smiling.

Ah, but its gonna cost you!

Here are some of the items you will need.

• One big expensive Enterprise Service Bus for all your infrastructural needs.
• Many application servers for those newly built services.
• Lots of training and consultancy from the "experts".
• EAI adapters for those troublesome legacy systems.
• One pilot project, probably of neglible business benefit.
• One Enterprise Architecture function to help with your systems governance.
• One SOA Center of Excellence.

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What is Service-Oriented Architecture - Canonical Data Model

You won't be doing Service-Oriented Architecture (SOA) for long before you encounter the concept of a Canonical Data Model (CDM). The idea is that you analyse your business processes, and derive a set of standard data types that you model using XML schema and use in your services - the Canonical Data Model. Perhaps you go one step further and bring in an industry model like IBM's IFW and use that as a starting point.

In the real world however, there is an estate of legacy systems that will tend to have a narrower view of data types than that proposed by the CDM. Some will only be interested in a particular aspect of the CDM types, some subset of the attributes, whereas others will have a different view completely. The issue is that there are different ways to model things.

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Agile SOA?

SOA promises business agility, so the question naturally arises whether Agile methodologies (as in XP, Scrum etc) are better suited to SOA development than more traditionaly (albeit iterative) methodologies such as RUP.

If you're not familiar with Agile principles you've probably been marooned on an island somewhere. Agile is the slated answer to the software development crisis. To quote the Agile Manifesto (http://www.agilemanifesto.org/principles.html):

We are uncovering better ways of developing software by doing it and helping others do it. Through this work we have come to value:

- Individuals and interactions over processes and tools
- Working software over comprehensive documentation
- Customer collaboration over contract negotiation
- Responding to change over following a plan

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