This paper focuses on the content analysis, a technique frequently used for the approach of issues concerning asynchronous computer mediated discussion groups in distance education.¶ Despite the fact that this research technique is frequently used, there are still no standards established. There is a variety of approaches, varying both at detail’s level and at the type of categories of analysis they use. In this paper the content category as a unit of analysis for the explanation of messages at the asynchronous distance education fora is presented, which is incorporated in the modelling in a formal language and the development of a respective system done by Hellenic Open University for this purpose.