Service Reference Model

Although specifically designed for Service Oriented Architecture, that is the IT delivery of services, the OASIS Reference Model for services [1] attempts to formalise many of the aspects of services and service delivery which can be useful in service modelling in general. This reference model defined service as:

“A service is a mechanism to enable access to one or more capabilities, where the access is provided using a prescribed interface and is exercised consistent with constraints and policies as specified by the service description”

The limitations in this definition are from its IT heritage. The terminology and emphasis on “prescribed interface”, “policies” and “service descriptors” are based on the formalist approach required by IT systems. However, it does capture the need to be accessible, and the importance of capabilities. This needs to be extended to say that the purpose of these capabilities is to create value for the service consumer.

ServiceConcepts.jpg

Relationships between Service Concepts — Adapted from [1]

The reference architecture also notes that the term service also includes the capability to perform work for another; the specification of the work offered for another and the offer to perform work for another.

The reference model then proceeds to identify more aspects or characteristics of the service which are important to all services – visibility, service description, contract & policy, execution context, interaction, and real world effect. The reference model continues by looking at the relationships between these concepts, and the sub-concepts to support these prime concepts.

Many of these concepts are important to understanding services from a business, as well as a technology, viewpoint. For example, a service needs to be reachable, whether it is supplied on-line over the internet, or the customer visits the showroom, or if the salesperson drives the demonstration car out to the customer’s own home. However, many IT formal descriptions become less defined in a business service model. “Shared state” can be implied, but not necessarily measured. Services interfaces may be through formal service level agreements, however, much of the interface may be implied of co-discovered.


References
1. OASIS SOA Reference Model Technical Committee 2008, Reference Model for Service Oriented Architecture, in OASIS (ed.), 1.0, Public Review Draft 1 edn, <http://docs.oasis-open.org/soa-rm/soa-ra/v1.0/soa-ra-pr-01.pdf>.
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