О проблеме логико-термальной эквивалентности недетерминированных стандартных схем программ
This book constitutes the refereed proceedings of the 13th International Haifa Verification Conference, HVC 2017, held in Haifa, Israel in November 2017. The 13 revised full papers presented together with 4 poster and 5 tool demo papers were carefully reviewed and selected from 45 submissions. They are dedicated to advance the state of the art and state of the practice in verification and testing and are discussing future directions of testing and verification for hardware, software, and complex hybrid systems.
Finite state transducers over semigroups can be regarded as a formal model of sequential reactive programs. In this paper we introduce a uniform tech- nique for checking eectively functionality, k-valuedness, equivalence and inclusion for this model of computation in the case when a semigroup these transducers op- erate over is embeddable in a decidable group.
Finite state transducers extend the finite state automata to model functions on strings or lists. They may be used also as simple models of sequential reactive programs. These programs operate in the interaction with the environment permanently receiving data (requests) from it. At receiving a piece of data such program performs a sequence of actions. When certain control points are achieved a program outputs the current results of computation as a response. It is significant that different sequences of actions may yield the same result. Therefore, the basic actions of a program may be viewed as generating elements of some appropriate semigroup, and the result of computation may be regarded as the composition of actions performed by the program. This paper offers an alternative technique for the analysis of finite state transducers over semigroups. To check the equivalence of two initial transducers we associate with them a Labeled Transition Systems (LTS). Each path in this LTS represents all possible runs of the initial transducers on the same input word. Every node of the LTS keeps track of the states of the initial transducers achieved at reading some input word and the deficiency of the output words computed so far. If both transducers reach their final states and the deficiency of their outputs is nonzero then this indicates that the initial transducers produce different images for the same word, and, hence, they are not equivalent. The nodes of the LTS that capture this effect are called rejecting nodes. Thus, the equivalence checking of the initial transducers is reduced to checking the reachability of rejecting nodes in the LTS. We show that one needs to analyze only a bounded fragment of the LTS to certify (un)reachability of rejecting nodes. The size of this fragment is polynomial of the size of the initial transducers if both transducers are deterministic, and single-exponential if they are k-bounded. The same approach is applicable for checking k-valuedness of transducers over semigroups.