Automated puzzle generation

We give a characterisation of certain types of puzzle in terms of the structure of the question posed and the nature of the answer to the puzzle. Using this characterisation, we have extended the HR theory formation system (2) to enable it to automatically generate puzzles given background information about a set of objects of interest. The main technical difficulty to overcome was to ensure that the puzzles generated by HR had a single solution (up to a level of plausibility). We give details of the implementation and some results from its application.