KAOS modelling: a short introduction
A KAOS model aggregates 4 complementary and interrelated views on the information system:
- the goals wished by the stakeholders involved in the information system: the owners, the users, the business managers, regulations, etc. and the requirements on the information that are needed in order to achieve these goals
- the inventory of human and automated agents located inside the system or belonging to its environment and to whom responsibility for achieving the requirements is assigned
- the problem domain in terms of domain concepts and relationships over those concepts
- the behaviour that those agents must undertake in order to achieve or maintian the requirements for which they are responsible.
The following figure displays the KAOS meta-model. The four views described above and their main constituents are shown. A KAOS model contains goals, requirements on the information system, expectations on the environment of this system, conflicts between goals, obstacles, entities, agents, etc.
Building a KAOS model can be assimilated to piece a jigsaw puzzle together; each item is identified from the information sources analysed and then progressively combined with the model elaborated so far.
The puzzle is fully assembled when the following conditions are fulfilled:
- each identified goal is refined in a set of requirements and/or expectations
- each requirement is put under the responsibility of a system agent and each expectation is put under the responsibility of an environment agent
- concepts used to describe the goals, requirements and expectations are defined in the Object model
- each requirement is associated with operations that the the agent responsable for this requirement has to perform in order to achieve or maintain the requirement.