Simulation for Symbolic Automata

Symbolické automaty sú podobné klasickým automatom s jedným veľkým rozdielom: prechody sú značené predikátmi definovanými v oddelenej teórii. Toto umožňuje použiť veľké abecedy s pouźitím oveľa menšieho miesta. V tejto práci sa zaoberáme výpočtom simulácie (binárnej relácie nad množinou stavov, ktorá aproximuje jazykovú inklúziu) pre tieto automaty. Táto relácia sa dá potom použiť pri redukovaní počtu stavov bez nutnosti determinizácie. Existuje niekoľko algoritomv pre výpočet simulácie pre Kripkeho štruktúry, ktoré boli neskôr modifikované pre označené prechodové systémy a klasické automaty. V tejto práci ukážeme ako sa dá jeden z týchto algoritmov modifikovať pre symbolické automaty použitím rozkladu domény abecedy ktorý je kompatibilný s predikátmi značiacimi prechody a použitím možností teórie abecedy.Symbolic automata are similar to classical automata with one big difference: transitions are labelled with predicates defined in separate logical theory. This allows usage of large alphabets while taking less space. In this work we are interested in computing simulation (a binary relation on states that language inclusion) for these automata. This can be then used for reducing the size of automata without the need to determinize them first. There exist few algorithms for computing simulation over Kripke structures, which were then altered to work over labeled transition systems and classical automata. We show how one of these algorithms can be modified for symbolic automata by using the partition of the alphabet domain that is compatible with the predicates labelling transitions and by using the possibilities of the alphabet theory.

Reasoning about Regular Properties: A Comparative Study

Several new algorithms for deciding emptiness of Boolean combinations of regular languages and of languages of alternating automata (AFA) have been proposed recently, especially in the context of analysing regular expressions and in string constraint solving. The new algorithms demonstrated a significant potential, but they have never been systematically compared, neither among each other nor with the state-of-the art implementations of existing (non)deterministic automata-based methods. In this paper, we provide the first such comparison as well as an overview of the existing algorithms and their implementations. We collect a diverse benchmark mostly originating in or related to practical problems from string constraint solving, analysing LTL properties, and regular model checking, and evaluate collected implementations on it. The results reveal the best tools and hint on what the best algorithms and implementation techniques are. Roughly, although some advanced algorithms are fast, such as antichain algorithms and reductions to IC3/PDR, they are not as overwhelmingly dominant as sometimes presented and there is no clear winner. The simplest NFA-based technology may be actually the best choice, depending on the problem source and implementation style. Our findings should be highly relevant for development of these techniques as well as for related fields such as string constraint solving