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.

More information on the KAOS methodology can also be obtained in a dedicated KAOS page on the UCL Web site or on the Objectiver Web site.