This chapter describes two programs which perform qualitative spatial reasoning using qualitative scene information. Each program can solve a basic spatial reasoning problem. The reason for constructing these programs was to test the capabilities of qualitative spatial representations in problem solving tasks, and this chapter discusses the grounds on which the two representations in the last chapter were evaluated.
The tasks used to test these representations were described in the introduction. One task is to find out what surfaces a moving object can come into contact with when it is sliding around a number of obstacles. The other is to plan a path for a moving object through a group of stationary obstacles, and into free space. The program which solved the first of these tasks used the ASSF representation, but it could equally well have been based on EPB/PDO. The program which solved the path planning problem used the EPB/PDO representation.
The programs described were both implemented in the LISP language, and some mention is made of language related matters in this chapter. This is because the descriptions of my programs are intended to be sufficiently detailed to make another implementation possible. The level at which description is carried out, however, does not extend to lisp coding details, and it should be possible to implement a similar system in a language other than LISP by using this chapter as a reference.