The paper describes the use of XML for creating an application oriented to the design and the implementation of Internet courses, that is an authoring tool whose main characteristic is the capability of producing on-line courses with a structure and an organisation of the contents that reflects a previously defined educational methodology.

The main requirements of such an authoring tool are the ease of use (for the teacher-author, whose competencies in general do not include professional computer skills), the ease of maintenance (for the site administrator) and, most of all, the flexibility and the adaptability of the contents (for the student-user).

We believe that on-line courses should be flexible enough to adapt to a number of different user profiles, that have different entry levels in terms of already acquired knowledge, and different learning goals. The course is a collection of different, self-consistent modules, and each module is composed of many sub-modules, that follow a different approach toward the contents to be taught, and offer different presentation formats. The main idea is to offer the students different views of the same contents, according to their profile.