Skill set analysis in knowledge structures.

We extend the theory of knowledge structures by taking into account information about the skills a subject has. In the first part of the paper we exhibit some structural properties of the skill-problem relationship and consequences for the interpretation of concurrent theories in terms of the skill theory. The second part of the paper offers a test theory based on skill functions: we present measurements for the data consistency of the skill-problem relationship, and estimate abilities in terms of lower and/or upper boundaries of problem states and skills, given a special instance of the skill-problem relationship. Some practical considerations are discussed, which enable the user of a skill-based system to optimize a partial theory about the skill-based behaviour of subjects based on empirical results.