Linking Notations and Theories in a Proof Tool

The formal development of non-trivial, real-time systems can be made more manageable by using several complementary formal methods for diierent aspects of the development. In this paper we show how sound interfaces between diierent methods can be deened formally in the HOL theorem proving system and how we have used such links to solve a variety of problems. Our motivation for linking theories is pragmatic. In a number of case studies diierent theories have been linked in order to make speciication and veriication more manageable and even to make it feasible. This paper ooers a formal framework for deening and implementing links between theories. Because both object language and meta language are visible in the HOL system, and the system itself can communicate with other systems, it is possible to deene explicitly and formally links of diierent \weight".