Formal language

About: Formal language is a research topic. Over the lifetime, 5763 publications have been published within this topic receiving 154114 citations.

High-Level Timed Petri Nets as a kernel for executable specifications

Abstract: One of the goals of the IPTES environment is to provide a highly usable and formally based specification support environment for real-time applications. Therefore the environment is built upon a formal language that provides a sound, and mathematically well-defined kernel for IPTES. The language provides a means for formulating unambiguous specifications that can be formally verified at any stage of the project. The ability of verifying the specifications from the early stages of the project is very important for revealing errors when their correction can be done at a much lower cost compared with the cost of removing the same errors in later phases. The formal kernel of IPTES is a class of high-level Petri nets, called HLTPNs (High-Level Timed Petri Nets), that allow specifications to be executed, simulated, tested and formally proved. HLTPNs come in two forms: the internal form (HLTPN i ) and the abstract form (HLTPN a ).HLTPN i may be viewed as the machine language of the abstract machine underlying the IPTES environment.HLTPN a provides a higher-level intermediate notation that allows to deal explicitly with aspects related to scheduling of the modeled system.

Logic and Rational Languages of Words Indexed by Linear Orderings

Abstract: We prove that every rational language of words indexed by linear orderings is definable in monadic second-order logic. We also show that the converse is true for the class of languages indexed by countable scattered linear orderings, but false in the general case. As a corollary we prove that the inclusion problem for rational languages of words indexed by countable linear orderings is decidable.

Congruence for SOS with data

Abstract: While studying the specification of the operational semantics of different programming languages and formalisms, one can observe the following three facts. Firstly, Plotkin's style of structured operational semantics (SOS) has become a standard in defining operational semantics. Secondly, congruence with respect to some notion of bisimilarity is an interesting property for such languages and it is essential in reasoning about them. Thirdly, there are numerous languages that contain an explicit data part in the state of the operational semantics. The first two facts have resulted in a line of research exploring syntactic formats of operational rules to derive the desired congruence property for free. However, the third point (in combination with the first two) is not sufficiently addressed and there is no standard congruence format for operational semantics with an explicit data state. In this paper, we address this problem by studying the implications of the presence of a data state on the notion of bisimilarity. Furthermore, we propose a number of formats for congruence.

Efficient context-free grammar constraints

Abstract: With the introduction of constraints based on finite automata a new line of research has opened where constraints are based on formal languages. Recently, constraints based on grammars higher up in the Chomsky hierarchy were introduced. We devise a time- and space-efficient incremental arc-consistency algorithm for context-free grammars. Particularly, we show how to filter a sequence of monotonically tightening problems in cubic time and quadratic space. Experiments on a scheduling problem show orders of magnitude improvements in time and space consumption.