Adriano Peron

Equivalences of Statecharts

We present a new semantics of Statecharts that excludes failures and a compositional formulation of this semantics based on Labelled Transition Systems (LTS). We consider a hierarchy of LTS equivalences and we study their congruence properties w.r. to statechart operators.

A Graph Rewriting Framework for Statecharts Semantics

The purpose of the paper is to show that graph rewriting is a suitable environment to formalize semantics of specification languages with dynamic features. This is exemplified considering Statecharts in a variant allowing dynamic creation of processes. Graph rewriting rules give the semantics of Statecharts in such interpretation. Standard Statecharts semantics can be recovered by suitably restricting derivation sequences that describe behaviours in the dynamic semantics. More abstract semantics, better suited to study equivalences and general properties, can be obtained from graph rewriting semantics.

Decidable Theories of ω-Layered Metric Temporal Structures

This paper focuses on decidability problems for metric and layered temporal logics. We prove the decidability of both the theory of metric temporal structures provided with an infinite number of arbitrarily coarse temporal layers and the theory of metric temporal structures provided with an infinite number of arbitrarily fine temporal layers. The proof for the first theory is obtained by reduction to the decidability problem of an extension of S1S which is the logical counterpart of the class of ω-languages accepted by systolic tree automata. The proof for the second one is done through the reduction to the monadic second-order decidable theory of k successors SkS

Timed cooperating automata

We propose Timed Cooperating Automata (TCAs), an extension of the model Cooperating Automata of Harel and Drusinsky, and we investigate some basic properties. In particular we consider variants of TCAs based on the presence or absence of internal activity, urgency and reactivity, and we compare the expressiveness of these variants with that of the classical model of Timed Automata (TAs) and its extensions with periodic clock constraints and with silent moves. We consider also closure and decidability properties of TCAs and start a study on succinctness of their variants with respect to that of TAs.

Transitions as Interrupts: A New Semantics for Timed Statecharts

Statecharts is a visual formalism for the specification of reactive systems. The formalism has been endowed with a “step-semantics” which heavily bounds the complexity of the reaction in a step, does not model interrupts in a natural way and is not proper for investigating refinement. In this paper, a new model is proposed allowing to overcome the mentioned drawbacks. From a syntactic point of view statecharts are generalized by introducing real time features like delays and timeouts. Though occurrencies of actions are related to a dense time domain, the behaviour of statecharts is forced to be discrete. Classes of statecharts are investigated which intrinsically behave discretely.

Statecharts, Transition Structures and Transformations

Statecharts are state-transition machines endowed with hierarchy on states and parallelism on transitions. It is shown that a statechart is described by a pair of relations over transitions (a transition structure), the former describing causality and the other describing a notion of asymmetric independence. A statechart can be effectively constructed from its transition structure. Transition structures corresponding to a subclass of Statecharts are characterized. Natural notions of morphisms among transition structures allow to define classes of statechart transformations which preserve behaviour.

Low-level processing techniques in geophysical image interpretation

Abstract The low-level processing modules of a knowledge based system for seismic-reflection image interpretation are presented; details on their functional and structural characteristics are also given. Results of the application of each module to real image data are extensively discussed, as well as the performances of the processing scheme as a whole.

Retiming Techniques for Statecharts

We consider a version of Statecharts having transitions with durations. We relate occurrences of transitions with a dense time domain and enforce a strong time semantics. We examine how durations associated with transitions can be changed while preserving behaviour (a retiming). We discuss also how a class of changes of the temporal feature of the environment (i.e. from non-discrete to discrete and vice-versa, shift, speed-up and slow-down) affect behaviour.

Systolic tree ω-languages

The class of ω-languages recognized by systolic tree automata is introduced. That class extends the class of Buchi ω-languages and is closed under boolean operations. The emptiness problem for systolic tree automata on infinite sequences is decidable. A characterization of systolic tree ω-languages in terms of a (suitable) concatenation of (finitary) systolic tree languages is also provided.

A Logical Characterization of Systolic Languages

In this paper we study, in the framework of mathematical logic, ℒ(SBTA) i.e. the class of languages accepted by Systolic Binary Tree Automata. We set a correspondence (in the style of Buchi Theorem for regular languages) between ℒ(SBTA) and MSO[Sig], i.e. a decidable Monadic Second Order logic over a suitable infinite signature Sig. We also introduce a natural subclass of ℒ(SBTA) which still properly contains the class of regular languages and which is proved to be characterized by Monadic Second Order logic over a finite signature Sig′ ⊂ Sig. Finally, in the style of McNaughton Theorem for star free regular languages, we introduce an expression language which precisely denotes the class of languages defined by the first order fragment of MSO[Sig′].