Yuri Gurevich

Learn More
We examine sequential algorithms and formulate a sequential-time postulate, an abstract-state postulate, and a bounded-exploration postulate . Analysis of the postulates leads us to the notion of sequential abstract-state machine and to the theorem in the title. First we treat sequential algorithms that are deterministic and noninteractive. Then we consider(More)
We prove that the three extensions of first-order logic by means of positive inductions, monotone inductions, and so-called non-monotone (in our terminology, inflationary) inductions respectively, all have the same expressive power in the case of finite structures. As a by-product, the collapse of the corresponding fixed-point hierarchies can be deduced.
The Abstract State Machine Language, AsmL, is a novel executable specification language based on the theory of Abstract State Machines. AsmL is object-oriented, provides high-level mathematical data-structures, and is built around the notion of synchronous updates and finite choice. AsmL is fully integrated into the .NET framework and Microsoft development(More)
DKAL is a new declarative authorization language for distributed systems. It is based on existential fixed-point logic and is considerably more expressive than existing authorization languages in the literature. Yet its query algorithm is within the same bounds of computational complexity as e.g. that of SecPAL. DKAL's communication is targeted which is(More)
I am delighted to open the rst workshop devoted entirely to evolving algebras. For the sake of brevity, I shorten the term \evolving algebra" to \ealgebra" (pronounce e-algebra) or \EA". The main goal of the evolving algebra methodology is to provide succinct and executable formal speci cations for algorithms. Here the term algorithm is taken in a broad(More)
In 1969 Rabin introduced tree automata and proved one of the deepest decidability results. If you worked on decision problems you did most probably use Rabin's result. But did you make your way through Rabin's cumbersome proof with its induction on countable ordinals? Building on ideas of our predecessors-&-mdash;and especially those of(More)
We give an algorithm that derives a finite state machine (FSM) from a given abstract state machine (ASM) specification. This allows us to integrate ASM specs with the existing tools for test case generation from FSMs. ASM specs are executable but have typically too many, often infinitely many states. We group ASM states into finitely many hyperstates which(More)
We present formal operational semantics for the C programming language. Our starting point is the ANSI standard for C as described in [KR]. Knowledge of C is not necessary (though it may be helpful) for comprehension, since we explain all relevant aspects of C as we proceed. Our operational semantics is based on evolving algebras. An exposition on evolving(More)