The ability to write good interactive questions is at the centre of CAA. It has some similarities to other forms of OU writing such as in-text questions (ITQs) and self-assessment questions (SAQs), and can be considered to be part of the e-Learning skill-set.
Too often the technical restrictions of CAA systems appear to restrict authors' ambitions in stretching their students, but CAA can be used for more than checking students' recall of facts. The original OpenMark design was deliberately not constrained by existing technical restrictions. Instead it was built around question formats supplied by the S103 Discovering Science course team. If it doesn't stretch the analogy too far we would like to compare the creation of the OpenMark system to the tactical conversation held between Barry John and Gareth Edwards prior to their first teaming together in a Welsh trial. Edward's account has it that John simplified tactics down to "you throw it, and I'll catch it". In a nutshell that was the S103/OpenMark relationship. OpenMark is a response to OU academics' requests.
Follow your predecessors and aim to move up Bloom's taxonomy of recall < comprehension < application < analysis < synthesis < evaluation. OpenMark can collect all student responses and will provide you with an analysis of how effective your question is in testing your students.
The exemplars on this site show what can be done.