Semiotic and discursive variables in cas-based didactical engineering

This paper presents a semiotic analysis of the (often claimed) potential of computer algebra systems (CAS) for enabling mathematical activity on a conceptual level higher than usual. Theoretical points are illustrated by examples from a development project in the context of a first year university course on calculus. We also discuss how they may be used in `a posteriori' didactical analysis and in didactical engineering. This revised version was published online in August 2006 with corrections to the Cover Date.