Closeness and Distance Relations in Order of Magnitude Qualitative Reasoning via PDL

The syntax, semantics and an axiom system for an extension of Propositional Dynamic Logic (PDL) for order of magnitude qualitative reasoning which formalizes the concepts of closeness and distance is introduced in this paper. In doing this, we use some of the advantages of PDL: firstly, we exploit the possibility of constructing complex relations from simpler ones for defining the concept of closeness and other programming commands such as while . . . do and repeat . . . until; secondly, we employ its theoretical support in order to show that the satisfiability problem is decidable. Moreover, the specific axioms of our logic have been obtained from the minimal set of formulas needed in our definition of qualitative sum of small, medium and large numbers. We also present some of the advantages of our approach on the basis of an example.