Disjunctive Modal Transition Systems Research Articles

Logical vs. behavioural specifications

There are two fundamentally different approaches for specifying and verifying properties of systems. The logical approach makes use of specifications given as formulae of temporal or modal logics and relies on efficient model checking algorithms; the behavioural approach exploits various equivalence or refinement checking methods, provided the specifications are given in the same formalism as implementations.In this paper we provide translations between the logical formalism of ν-calculus and the behavioural formalism of disjunctive modal transition systems. The translations preserve structural properties of the input specification and allow us to perform logical operations on the behavioural specifications as well as behavioural compositions on logical formulae. The unification of both approaches provides additional methods for component-based stepwise design.

A linear-time–branching-time spectrum for behavioral specification theories

We propose behavioral specification theories for most equivalences in the linear-time–branching-time spectrum. Almost all previous work on specification theories focuses on bisimilarity, but there is a clear interest in specification theories for other preorders and equivalences. We show that specification theories for preorders cannot exist and develop a general scheme which allows us to define behavioral specification theories, based on disjunctive modal transition systems, for most equivalences in the linear-time–branching-time spectrum.

Compositionality for quantitative specifications

We provide a framework for compositional and iterative design and verification of systems with quantitative information, such as rewards, time or energy. It is based on disjunctive modal transition systems where we allow actions to bear various types of quantitative information. Throughout the design process, the actions can be further refined and the information made more precise. We show how to compute the results of standard operations on the systems, including the quotient (residual), which has not been previously considered for quantitative non-deterministic systems. Our quantitative framework has close connections to the modal nu-calculus and is compositional with respect to general notions of distances between systems and the standard operations.

Modal Interface Automata

De Alfaro and Henzinger's Interface Automata (IA) and Nyman et al.'s recent combination IOMTS of IA and Larsen's Modal Transition Systems (MTS) are established frameworks for specifying interfaces of system components. However, neither IA nor IOMTS consider conjunction that is needed in practice when a component shall satisfy multiple interfaces, while Larsen's MTS-conjunction is not closed and Bene\v{s} et al.'s conjunction on disjunctive MTS does not treat internal transitions. In addition, IOMTS-parallel composition exhibits a compositionality defect. This article defines conjunction (and also disjunction) on IA and disjunctive MTS and proves the operators to be 'correct', i.e., the greatest lower bounds (least upper bounds) wrt. IA- and resp. MTS-refinement. As its main contribution, a novel interface theory called Modal Interface Automata (MIA) is introduced: MIA is a rich subset of IOMTS featuring explicit output-must-transitions while input-transitions are always allowed implicitly, is equipped with compositional parallel, conjunction and disjunction operators, and allows a simpler embedding of IA than Nyman's. Thus, it fixes the shortcomings of related work, without restricting designers to deterministic interfaces as Raclet et al.'s modal interface theory does.

Comparing disjunctive modal transition systems with an one-selecting variant

An expressive class of abstractions for labeled transition systems is that of disjunctive modal transition systems ( DMTS ), featuring may- and must transitions as well as disjunctive hypertransitions ( OR). In order to describe exclusive choice adequately, we develop a variant of DMTS s called 1-selecting modal transition systems ( OMTS ) that, roughly speaking, interprets hypertransitions exclusively ( XOR). These abstract models, DMTS s and OMTS s, are compared with respect to their expressive power. By giving transformations or showing their non-existence, we show that the two setting can express the same sets of labeled transition systems, but 1-selecting modal transition systems have a richer refinement preorder.