Tuesday, 24 March 2009

CBDI Forum publish Rich Service Specification Template for SOA

The Service Specification is a pivotal SOA deliverable that enables both Service Provider and Consumer to share a common view of a Service’s behavior. However, despite the importance of Service Specification there is no widely adopted standard.

CBDI Forum first developed our Service Specification Template in 2005 and it has since been used on numerous projects by our customers and ourselves.

TOGAF have recently published a Service Specification that, whilst rather more high level, bears strong resemblance to the CBDI template.

Following several requests to make our template more widely available CBDI is making the Service Specification Template freely available to the public under licence.

The template is now available for download

The Service Specification Template is designed to address the following requirements

Contract First Delivery
One of the important principles of SOA is that of contract-first delivery, and this is one of the principles that motivates and drives the need for a Service Specification.
Contract-first means the specification of the service should precede development of its implementation.

Use in Multiple Roles
The Service Consumer will of course want to know exactly what the service does. They will want to know what behaviour it offers, and what they have to do in order to use the Service.
A Service Provisioner whose role it is to locate a suitable Service will need to be able to compare the available Services against a specification to see if it meets requirements. Or if they are commissioning a new Service (or implementation of) they will need to precisely detail the required behavior of that Service.
Hence, the developer in the Service Providing organization who has to build an implementation of the Service also needs to know what requirements need to be meet.
A Service Specification is an implementation-neutral deliverable that contains all the information necessary to meet all these needs.
The Service Specification facilitates exchange of consistent and precise instructions between different participants in the Service supply chain

The Service Lifecycle
The Service Specification is expected to be developed iteratively across the service lifecycle. For example, as a;
Planned Service it may start as a high-level description of requirements
Specified Service it will provide precise detail of the required behaviour
Provisioned Service it may reflect any choices or compromises that have been made in the provisioning process, that diverge from the ideal specification
Deployed Service it will detail the actual endpoints and other aspects required to use the service at runtime

Using the Service Specification Template
CBDI provides templates for various SAE deliverables as Word documents. However, we do not really expect users to then complete and store instances of those documents using Word. Rather, they should treat them as the basis for schemas from which they could create a database to store the data in a more structured way – for example in some form of Service Catalog. Our Word templates might then be better used as a format in which to report from that database, rather than the place in which the data is itself stored.

For example, the Operation Signatures would be held as WSDL documents, and the Service Information Model might be held as a UML Class diagram in a modelling tool.

Further guidance on this is provided in two CBDI Journal Reports
Service Lifecycle Automation
Service Lifecycle Configuration Management

The template itself is only part of the story however. The delivery of a Service Specification is just one step, mid way through the CBDI-SAE SO Process.
Though the Service Specification Template is fully documented, ideally further guidance in its use is required.

CBDI have published Service Specification guidance in the CBDI Journal (gold subscribers), and further process guidance is also provided in the SAE Knowledgebase.
Practical Service Specification and Design Part 3: Specifying Services
Documenting Service Behavior
Process Logic and the Identification of Service Behavior
Produce Service Specification (SAE Process Unit) (platinum suscribers only)

We invite discussion on the Service Specification Template via CBDI LinkedIn

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