How, what, when and why SOA?

After taking part in a recent discussion on SOA, I would like to say that SOA doesn't answer the questions How, What or even When in terms of use, but do answer the question Why.

How?
There is a misunderstanding that SOA has something to do with how people should implement their services or group them in types of service behaviors. SOA makes no difference between services implementing master-data, processes, use-cases, entities, identities, rules, or legacy adapters nor does it care. To SOA a service is just a service.

What?
SOA doesn't require a specific message-passing technology but Web Services is preferred for obvious reasons.

When?
SOA is not suitable in all situations - but that isn't up to SOA to decide. The answer here is dependent upon the how and the what described above.

Why?
SOA answer the why-question with - to achieve business agility. Not by how services are implemented or with what technology is used, but with service management - the things that happens between the 2 service endpoints during a call. Things like versioning, routing, filtering, virtualization, en/decryption, en/decoding, monitoring, transformation, logging, translation, billing, validation, etc - all packaged in a nice runtime governance tool.

Why patterns?!

Why can't you find a polymorphic pattern for OOD? Because it's so obvious!

Polymorphism is part of the paradigm and part of the oo-languages. It's not obvious how to use polymorphism, but there are no patterns describing it. Design patterns seems to concern ideas not really aimed for a specific software paradigm. I been thinking why patterns play such an important role today. It's just my believe that where ever there is a pattern, there is a shortcoming in the underlying paradigm/languages to solve a specific problem. I'm joining in criticism of patterns.

Cutting slices from a blob

I liked the way Mats Helander described service-orientation. To understand the good thing about SOA you really need to see it from the business perspective. From a 10000' view, IT really looks like a big blob. On a 1000' view, you can discern smaller blobs which are applications (aka black boxes or silos). The SOA will help breaking up the applications in small services that can be composed into new services based on policies. The selection for how the services will be used in a composition is up to the heart of the SOA - the mediation layer. The mediation layer (such as WCF or Synapse) will make sure that the policies are applied correctly.

Some people claims that service composition (orchestration) is part of the SOA paradigm. I would rather give credit to BPM for techniques related to service composition.

A Business-Oriented Architecture

While some people keep fighting for their knowledge domain, the world change around them. I'm talking about program languages, design tools and runtime engines, still using object-orientation as a model for implementing a business critical system. Since the early 90th object-oriented architectures have been the main technology platform for building solutions for business. What we got with us from those years is that technology driven view point of software development is bad. Whether an object-centric perspective helped the programmers understand the business or not isn't relevant. What we do know is that noone else understood the object model. Lot of initiatives have tried to bridge between the business and the OO model. Most of them have just made it worse, with really high cost as a result for software development.

No, there's a need for a new, better model for designing software. Something that the business can relate to, something that everyone can relate to. Processes and services are keys to this new model. We have all heard all the great stuff we can do with SOA and BPM, but what are the differences and can they play together?



A process-oriented architecture (POA) fits a company that's frequently changing and improving their business processes. This architecture supports a process improvement life cycle where bottle necks and bad design are found and adjusted using analyzis tools. A POA is a platform using a transparent model for business processes that aligns the business with IT very well.

A service-oriented architecture (SOA) on the other hand suites a company reorganizing their business structure frequently (such as out-sourcing, mergers and acquisitions, internal reorginization, etc). The main goal with a SOA is to control the services based on policies. These policies are defined in the service management framework. A SOA gives the agility in a business where services easily can be controlled from using service governance. A SOA will provide the virtual service mediation layer between the service consumer and the service producer where loosely coupling is crucial.

Normally a company would agree that both transparency and agility is important for their business. The only way to achieve this is by taking the road from OOA to a business-oriented architecture (BOA). This is a platform where the best from BPM and SOA is combined. People from the BPM community call this platform BPM 2.0, while some call it SOA 2.0. I think something neutral as BOA is more diplomatic.

The next question would be to ask which way is more natural to go from OOA to BOA, the red or the blue road. I would say the red because SOA is the foundation for a successfull POA.