Top-down Approach

  One of our main requirements is to develop a scenario independent service model. For this purpose we use a methodology, which is following an object oriented development style (comparable to UML). This results in the top-down approach depicted in figure , which is used to identify the elements of this model.

[Analysis method]Analysis method   [r]An inherent characteristic of every service is that it involves two major players: one offering and one requesting the service. Speaking in technical terms there is a provider side and a customer side. Both interact to accomplish a service. By solely examining these interactions we are able to draw conclusions about the service functionality without the need to take the service implementation into account. Therefore, it is important to identify these interactions for which we use a service life cycle.

As it is impossible to find every single interaction regarding all possible services, an abstraction of these interactions is needed. Thus, we use classes to group the interactions. The life cycle phases lead to a first grouping of the interactions. To refine this rough structure, a functional classification (based on TMF's TOM [#!smart-tmn-tom99!#] and OSI's Systems Management Functional Areas [#!iso10040!#]) is performed in addition. The combination of these two activities leads to a classification matrix.

After all, as interactions take place between a pair of roles representing e.g., organizational units on both sides, roles are assigned to interaction classes.

By examining the identified interaction classes and roles, we are able to specify interfaces as well as entities participating in service provisioning. This leads to the final step of our analysis method: developing a service model containing objects and relations on basis of the former identified interactions, interfaces and roles. This step also encloses a recursive application of the model to represent provider hierarchies.

The remainder of this section applies the described methodology to examine interactions and to identify interaction classes and roles. In section these entities are used to develop a service model.