Service Design - Are You A SOA Poser or a Com-Poser?

Up until now, there has been such a rush to roll out initial SOA services and supporting infrastructure, that little attention has been given to what good service design truly entails.  This is a natural evolution that must occur with any technology or methodology.  Throughout this summer, I plan on releasing several posts regarding proper service design.

Initially, I would like to focus on the subject of ‘composability’.  Composable services have several important qualities:

• composable services stictly adhere to their service interface, Service Level Agreements(SLAs), and supporting metadata
• service operations always leave enterprise data in a valid business state
• service operations can be called indepently, in parallel, or as a part of a larger service orchestration
• service operations can be called within or without a transaction context

When you boil it down to the essentials, composable services clearly define what they do and they do exactly what they have defined.  Consumers of composable services are then at liberty to determine how they want to use that service’s operations, rather than the service having certain built-in assumptions regarding how the service will be used or what the larger business context ought to be.

To learn more about the merits and details of composable services, I recommend the following resources:

• “Composable Services” (MSDN Library)
• “Service Composability” (SOAprinciples.com)
• “A Composable Service is a Good Service” (Presentation at SOAWorld 2008 next week)

There’s another, less tangible benefit of composable services — they are lower stress.  The frustration and stress associated with consuming a service that later fails due to some unknown buisiness logic violation is supremely frustrating.  Consuming services that are not composable is stressful, because they cannot be depended upon to work in whatever context you choose.  Likewise, publishing non-composable services for consumption is stressful because the service provider is constantly in fear that someone will ‘misuse’ a service.  This is no way to run an enterprise or encourage the adoption of service orientation. 

I’ll explore all of these topics next week in my presentation at SOAWorld on composable services.  I’ll post the completed presentation as well as perspectives from the audience next week.  Have a great weekend and I’ll see you in New York!

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• Title: Service Design - Are You A SOA Poser or a Com-Poser?
• Written on: June 19th, 2008
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Kyle Gabhart is the Director of Emerging Technologies for Web Age Solutions, a leading provider of Custom IT Education and Mentoring. He has extensive experiencing in designing, aligning, developing, and managing Enterprise Architectures for organizations of all shapes and sizes. Kyle frequently writes and speaks for international audiences and occasionally people listen.

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