Distinguishing experiments for timed nondeterministic finite state machine

The problem of constructing distinguishing experiments is a fundamental problem in the area of finite state machines (FSMs), especially for FSM-based testing. In this paper, the problem is studied for timed nondeterministic FSMs (TFSMs) with output delays. Given two TFSMs, we derive the TFSM intersection of these machines and show that the machines can be distinguished using an appropriate (untimed) FSM abstraction of the TFSM intersection. The FSM abstraction is derived by constructing appropriate partitions for the input and output time domains of the TFSM intersection. Using the obtained abstraction, a traditional FSM-based preset algorithm can be used for deriving a separating sequence for the given TFSMs if these machines are separable. Moreover, as sometimes two non-separable TFSMs can still be distinguished by an adaptive experiment, based on the FSM abstraction we present an algorithm for deriving an r-distinguishing TFSM that represents a corresponding adaptive experiment

Deterministic Timed Finite State Machines: Equivalence Checking and Expressive Power

There has been a growing interest in defining models of automata enriched with time. For instance, timed automata were introduced as automata extended with clocks. In this paper, we study models of timed finite state machines (TFSMs), i.e., FSMs enriched with time, which accept timed input words and generate timed output words. Here we discuss some models of TFSMs with a single clock: TFSMs with timed guards, TFSMs with timeouts, and TFSMs with both timed guards and timeouts. We solve the problem of equivalence checking for all three models, and we compare their expressive power, characterizing subclasses of TFSMs with timed guards and of TFSMs with timeouts that are equivalent to each other.Comment: In Proceedings GandALF 2014, arXiv:1408.556

PROGRESSIVE SOLUTIONS TO FSM EQUATIONS

Abstract. The equation solving problem is to derive the behavior of the unknown component X knowing the joint behavior of the other components (or the context) C and the specification of the overall system S. The component X can be derived by solving the Finite State Machine (FSM) equation C ◊ X ∼ S, where ◊ is the parallel composition operator and ∼ is the trace equivalence or the trace reduction relation. A solution X to an FSM equation is called progressive if for every external input sequence the composition C ◊ X does not fall into a livelock without an exit. In this paper, we formally define the notion of a progressive solution to a parallel FSM equation and present an algorithm that derives a largest progressive solution (if a progressive solution exists). In addition, we generalize the work to a system of FSM equations. Application examples are provided

Синтез тестов с гарантированной полнотой для недетерминированных временных автоматов

Nowadays, the behaviour of many systems can be properly described by taking into account time constraints, and this motivates the adaptation of existing Finite State Machine (FSM)- based test derivation methods to timed models. In this paper, we propose a method for deriving conformance tests with the guaranteed fault coverage for a complete possibly nondeterministic FSM with a single clock; such Timed FSMs (TFSMs) are widely used when describing the behaviour of software and digital devices. The fault domain contains every complete TFSM with the known upper bounds on the number of states and finite boundary of input time guards. The proposed method is carried out by using an appropriate FSM abstraction of the given TFSM; the test is derived against an FSM abstraction and contains timed input sequences. Shorter test suites can be derived for a restricted fault domain, for instance, for the case when the smallest duration of an input time guard is larger than two. Moreover, the obtained test suites can be reduced, while preserving the completeness, when all input time guards of the specification and an implementation are right closed (or all intervals are left closed). Experiments are conducted to study the length of test suites constructed by different methods.В настоящее время при описании поведения дискретных систем достаточно часто необходимо принимать во внимание временные аспекты, и соответственно появляется необходимость в распространении автоматных методов синтеза тестов с гарантированной полнотой на временные автоматы. В данной статье мы предлагаем метод построения проверяющих тестов с гарантированной полнотой для полностью определенного, возможно, недетерминированного автомата с одной временной переменной. Такие временные автоматы используются при описании поведения программного обеспечения и цифровых устройств. Область неисправности содержит все полностью определенные автоматы с заданным числом состояний и известной верхней оценкой на интервалы, описывающие временные ограничения. Предлагаемый метод опирается на построение по заданному временному автомату соответствующей конечно автоматной абстракции (абстрактного автомата). По абстрактному автомату строится проверяющий тест, последовательности которого суть временные входные последовательности. Более короткие тесты можно построить, если ввести дополнительные ограничения на область неисправности, например, для случая, когда известна наименьшая продолжительность каждого временного интервала в тестируемой реализации, и её величина больше двух. Кроме того, тест можно сократить с сохранением его полноты в случае, когда все интервалы для временных ограничений закрыты справа (или все интервалы закрыты слева). Приводятся результаты проведенных компьютерных экспериментов по сравнению длин тестов, построенных по временному автомату различными методами.