Specification of Asynchronous Component Systems with Modal I/O-Petri Nets

With the aim to preserve deadlock freedom, we define a new refinement relation for modal transition systems (MTS), using an MTS-specific variant of testing in the sense of De Nicola and Hennessy. We characterize this refinement with a kind of failure semantics, and we show that it 'supports itself' e.g. in the sense of thoroughness -- in contrast to the standard modal refinement. We present a conjunction operator w.r.t. our new refinement, this operator is very different from others found in the literature, and it demonstrates that the conjunction of two MTSs is an MTS -- again in contrast to the case of modal refinement. Finally, we also consider a may-testing approach.

Modal transition systems (MTS) is a well-studied specification formalism of reactive systems supporting a step-wise refinement methodology. Despite its many advantages, the formalism as well as its currently known extensions are incapable of expressing some practically needed aspects in the refinement process like exclusive, conditional and persistent choices. We introduce a new model called parametric modal transition systems (PMTS) together with a general modal refinement notion that overcomes many of the limitations. We investigate the computational complexity of modal and thorough refinement checking on PMTS and its subclasses and provide a direct encoding of the modal refinement problem into quantified Boolean formulae, allowing us to employ state-of-the-art QBF solvers for modal refinement checking. The experiments we report on show that the feasibility of refinement checking is more influenced by the degree of nondeterminism rather than by the syntactic restrictions on the types of formulae allowed in the description of the PMTS.

In this paper, the synthesis of bounded Petri nets from deterministic modal transition systems is shown to be undecidable. The proof is built from three components. First, it is shown that the problem of synthesising bounded Petri nets satisfying a given formula of the conjunctive nu-calculus (a suitable fragment of the mu-calculus) is undecidable. Then, an equivalence between deterministic modal transition systems and a language-based formalism called modal specifications is developed. Finally, the claim follows from a known equivalence between the conjunctive nu-calculus and modal specifications.

Modal Transition System (MTS) is a well studied formalism for partial model specification. It allows a modeller to distinguish between required, prohibited and possible transitions. Disjunctive MTS (DMTS) is an extension of MTS that has been getting attention in recent years. A key concept for (D)MTS is refinement, supporting a development process where abstract specifications are gradually refined into more concrete ones. Refinement comes in different flavours: strong, observational (where \(\tau \)-labelled transitions are taken into account), and alphabet (allowing the comparison of models defined on different alphabets). Another important operation on (D)MTS is that of merge: given two models M and N, their merge is a model P which refines both M and N, and which is the least refined one.

Modal transition systems provide a behavioral and compositional specification formalism for reactive systems. We survey two extensions of modal transition systems: parametric modal transition systems for specifications with parameters, and weighted modal transition systems for quantitative specifications.

Symmetric and Asymmetric Asynchronous Interaction

In the setting of the modal logic that characterizes modal refinement over modal transition systems, Boudol and Larsen showed that the formulae for which model checking can be reduced to preorder checking, that is, the characteristic formulae, are exactly the consistent and prime ones. This paper presents general, sufficient conditions guaranteeing that characteristic formulae are exactly the consistent and prime ones. It is shown that the given conditions apply to various behavioural relations in the literature. In particular, characteristic formulae are exactly the prime and consistent ones for all the semantics in van Glabbeek's linear time-branching time spectrum.

A Petri net is confluent if its firing relation is confluent, i.e., for any two reachable markings there exists a marking reachable from both of them. We prove that confluence is a decidable property for Petri nets and it is preserved by asynchronous parallel composition. Applications to Petri net structural transformations and term rewriting systems are then pointed out.

Petri nets have been widely used in the design of embedded controllers, namely in electronic hardware and computing platforms design, as well as within automation application areas. This paper presents updated characteristics of one class of Petri nets, named Input-Output Place-Transition Petri nets (IOPT nets), extended to support networked embedded controllers design and globally-asynchronous locally-synchronous (GALS) systems modeling, together with its associated metamodel and execution semantics. The proposed meta-model is compliant with the Petri Net Markup Language (PNML) metamodel, augmented with the descriptions for inputs and outputs, as well as for time domains and communication channels. The meta-model is described using UML class diagrams and has an equivalent Ecore meta-model that positioning IOPT nets within the Eclipse Modeling Framework (EMF).

We propose a platform for the specification and analysis of systems. This platform contain models, their refinement and abstraction, and a temporal logic semantics; rendering a sound framework for property validation and refutation. The platform is parametric in a domain of view, an abstraction of a construction based on the Plotkin power domain. For each domain of view E, the resulting platform P [E]1 contains partial,incomplete systems and complete systems — the actual implementations. Complete systems correspond to the platform that has as parameter a domain D that is, as a set, isomorphic to the maximal elements of E. If one restricts P [E] to implementations, but retains the temporal logic semantics, refinement, and abstraction relations, one recovers the platform P [D]. This foundation recasts existing work on modal transition systems, presents fuzzy systems, and ponders on the nature of probabilistic platforms. For domains of view E that are determined by a linearly ordered, complete lattice, we present a category of “relations” as a step toward a view-based semantics of predicate logic.

Modern software systems are typically built of components that communicate through their external interfaces. A component's behavior can be effectively described using finite state automata-based formalisms (e.g., statecharts [5]). The basic formalism, labelled transition systems, describes the behavior of a component in terms of states and labeled transitions. The more advanced formalisms, such as modal transition systems and interface automata, extend LTS to incorporate additional information related to interface operation controllability — distinguishing between input, output, and internal actions — and the possible partiality of a component's specification — distinguishing between required and unknown (maybe) behaviors. Capturing the controllability and partiality aspects of a component's specification facilitates (1) checking interface compatibility, (2) checking whether one component can safely replace another component, and (3) checking whether one specification is a proper refinement of another specification. In this paper, we study the existing definitions of these three types of checks, and then exemplify their limitations in the context of modal interface automata (MIA); MIA is a class of component behavior specifications that incorporates both controllability and partiality information. We outline a set of enhancements to MIA as possible solutions to the identified limitations.

Internal communication has become a formal discipline in modern organizations also due to its proven impact on performance. Today, in the era of digitation and deepening the use of AI tools in organizations, communication is becoming more available and more tailored to organizational audiences. As a result, the scope of communication and internal communication expand. Accordingly, organizations manage a mix of communication channels and tools and refine the definition of the line manager’s role with internal communication. At the same time, the expansion of internal communication can lead to overload and loss of focus, as well as challenge the management ability of leading internal communication. This article presents the findings from a qualitative study that constitutes the first stage of a PhD-level research entitled: “The Relationship between Internal Communication and the Strength of Employees’ Engagement in Companies”. This current study examines the internal communication processes based on data collected through interviews with 7 managers and 7 employees. The study has identified three core themes within internal communication processes: communication skills of line managers, corporate communication, managing multiple communication tools and channels. Each theme illustrates a combination of key categories, i.e., knowledge and idea sharing, direct person-to-person communication. The study highlights the significant role of communication led by line managers, as 56.5% of interviewees used theme referring to their line manager when describing how they received the internal communication. This article highlights the pivotal role of line managers’ managerial communication skills in the delivery of internal communication and, expands knowledge about the required skills.

We survey the specification formalism of modal transition systems (MTS). We discuss various extensions of MTS, their relationships and modelling capabilities. The extensions include more involved modalities, quantitative aspects, or infinite state spaces. Further, we discuss problems arising in verification and analysis of these systems. We cover refinement checking, model checking and synthesis, standard logical and structural operations as used in specification theories as well as the respective tool support.

The idea to investigate the communication of the Council of Lithuania first came up after analysing the process of the representation of the Council of Lithuania from 21 September 1917 to 11 November 1918 and realising that internal and external communication was closely intertwined and each was important in its own way. The analysis of the communication of the Council of Lithuania is important for several reasons. Firstly, it helps to identify internal and external communication channels and to understand their role in establishing and maintaining close contacts with the local and foreign public; secondly, it provides an opportunity to see the actual scope of activities pursued by the Council of Lithuania and its Presidium, and, thirdly, it sheds light on the specificities of the functioning of the little-studied administrative apparatus of the Council of Lithuania. The aim of the study is to examine internal and external communication channels of the Council of Lithuania and to reveal the specificities of their functioning (21 September 1917–11 November 1918). To that end, the research made use of published (collections of documents, information in the press) and unpublished sources stored at the Lithuanian Central State Archives, the Manuscripts Department of the Wroblewski Library of the Lithuanian Academy of Sciences, the Political Archive of the German Foreign Office, and studies by historians and legal historians. The research covers the chronological period from 21 September 1917 to 11 November 1918, i.e., from the election of the Council of Lithuania during the Vilnius Conference (18– 23 September 1917) to the formation of the Provisional Government of Lithuania. Methods of qualitative analysis and synthesis (the new material of the sources was supplemented with the information circulating in historiography), the comparative method (the facts from Lithuanian and German archives and the press are compared), the descriptive and inductive methods were employed. To process the primary sources in Lithuanian and German languages, the logical-analytical method (analysis of the notional content and information) was applied. The research revealed that external and internal communication of the Council of Lithuania was the responsibility of the Presidium of the Council of Lithuania. Its members organised and coordinated internal communication through the head of the Central Office. The members of the Council of Lithuania used to communicate among themselves and with the members of the Presidium and exchanged information at official plenary sessions, verbally and in writing, by phone and telegraph. In exceptional cases, authorised persons and delegations served as intermediaries. Most problems in internal communication used to arise from the failure to provide information in writing (copies of documents not prepared, forwarded, or delivered in time) and belated invitations to the plenary sittings during the sessions of the Council of Lithuania. The members of the Presidium and the heads of the commissions and administrative divisions of the Council of Lithuania used to communicate and exchange information verbally (at sittings and meetings) and in writing (through letters, documentation). All direct and indirect channels available at that time were utilised for the Council’s external communication with local and foreign public, Lithuanians abroad, and German civil and military administration: (1) direct channels include visits to the Secretariat of the Council of Lithuania during the publicly- announced reception hours established by the members of the Presidium and the members of the commissions of the Council of Lithuania, meetings of the members of the Council of Lithuania with Lithuanian residents, their organisations, and the representatives of the German Military Administration in Lithuania (Militärverwaltung Litauen), conferences abroad, reception of the delegates (authorised representatives) of Lithuanians living abroad or delegations; (2) indirect channels comprise newspapers (they used to print reception hours, minutes of sittings, and other important information), letters and telegrams, and special information publications (Bėgamosios Lietuvos Tarybos žinios).

Given a labeled Petri net with silent (unobservable) transitions, we are interested in performing initial marking estimation in a probabilistic setting. We assume a known finite set of initial markings, each with some a priori probability, and our goal is to obtain the conditional probabilities of initial markings of the Petri net, conditioned on an observed sequence of labels. Under a Markovian assumption on the probabilistic model, we develop a recursive algorithm that allows us to efficiently determine the conditional probabilities for each possible initial marking (conditioned on the sequence of observations seen so far). We illustrate the proposed methodology via an example and discuss potential applications in the context of initial state opacity for security applications.