The process of designing and developing Computer Assisted Learning (CAL) resources has been the subject of much debate within the educational technology field. Past models have tended to draw on one of two broad areas of research: Instructional Design (or Curriculum Design) and Software Engineering (or Information System Design). More recently, the trend away from 'instructivist' theories of learning and towards constructivist theories has become central to this debate.

During this work-in-progress presentation a model for the design and development of constructivist CAL resources will be proposed. The model draws on aspects of both Instructional Design and Software Engineering research. The model also draws on earlier work, which proposed a classification scheme for learner activities, and hypothesised connections between categories of learning outcome and categories of learner activity.

The following assumptions are implicit within the model:

• The development of learning resources should always begin with a clear statement of the intended learning outcomes;
  
• Learning occurs through the learner actively constructing their own knowledge representation, rather than through passively receiving information; and
  
• The only way to ensure that a piece of software achieves its' intended objectives is to ensure that users of the software (in this case the target learners) are involved throughout the design process.

The proposed model involves multiple cycles through the following stages:

i) analysis and specification,

ii) pedagogical design,

iii) software design,

iv) implementation and

v) evaluation.

Some characteristics of the proposed model are as follows:

• A central part of the pedagogical design process is a description of intended learner activities. This is consistent with the constructivist emphasis on the learner being active in the learning process. The use of a matrix connecting categories of learning outcome to categories of learner activity is proposed.
  
• The organisation of the materials into a cohesive whole is another important part of the pedagogical design process. This process is informed by constructivist principles.
  
• The result of the organisation of the materials will be a storyboard and a screen map. It is proposed that the storyboard will include, for each screen, a sketch of the layout, a list of the media elements, a list of the interactive elements and a description of the intended learner activities.
  
• Even though the model is described as a series of stages, the development process should be an iterative one, involving a number of cycles through the five stages. Specifically, a number of successive prototypes should be developed and each should be subject to a formative evaluation process. This approach draws on the rapid prototyping software engineering model.

This presentation is intended to fill two roles. Firstly, it is a contribution to instructional development research. Secondly, it provides a guide to prospective CAL resource developers and to this end, the use of the model in the design of a sample CAL system called Principles of Computer Graphics will be described.