Simulations Between Programs as Cellular Automata

We present cellular automata on appropriate digraphs and show that any covered normal logic program is a cellular automaton. Seeing programs as cellular automata shifts attention from classes of Herbrand models to orbits of Herbrand interpretations. Orbits capture both the declarative, model-theoretic meaning of programs as well as their inferential behavior. Logically and intentionally different programs can produce orbits that simulate each other. Simple examples of such behavior are compellingly exhibited with space-time diagrams of the programs as cellular automata. Construing a program as a cellular automaton leads to a general method for simulating any covered program with a Horn clause program

Applications of Formal Methods to Specification and Safety of Avionics Software

This report treats several topics in applications of formal methods to avionics software development. Most of these topics concern decision tables, an orderly, easy-to-understand format for formally specifying complex choices among alternative courses of action. The topics relating to decision tables include: generalizations fo decision tables that are more concise and support the use of decision tables in a refinement-based formal software development process; a formalism for systems of decision tables with behaviors; an exposition of Parnas tables for users of decision tables; and test coverage criteria and decision tables. We outline features of a revised version of ORA's decision table tool, Tablewise, which will support many of the new ideas described in this report. We also survey formal safety analysis of specifications and software

The authorization calculus

The Authorization Calculus is a modal logic with which to formally model systems that provide credentials that indicate privileges and make access control decisions based on those privileges. Extending an access control calculus of Abadi, Burrows, Lampson, and Plotkin with privileges gives us a formal way to reason about explicit privileges issued to principals that authorize access as well as such things as authorizing group membership and role activation. Formal deduction rules are used to create proofs that yield a sound foundational basis for making the access decision. We finalize by applying the Authorization Calculus for a formal analysis of the Common Object Request Broker Architecture (CORBA) Common Secure Interoperability Version 2 (CSIv2) Protocol