Process Algebra Research Articles

A process calculus for spiking neural P systems

This paper presents a calculus inspired by the spiking neural P systems. Its operational and denotational semantics are defined; they are related by using the metric semantics methodology, showing that the denotational semantics is correct with respect to the operational one. We use the continuations for concurrency to describe precisely the nondeterministic behaviour, the time delays between firings and spikings, as well as the synchronized functioning specific to spiking neural P systems.

On distributability

The Actor model of computation is the backbone for the design of some of the most successful distributed programming platforms, Erlang and Akka. It builds upon asynchronous message-passing (liberating senders from waiting) and unique message-routing (using unique Actor addresses), which enables relatively simple distributed implementations. The Actor model shares these principles with the model of computation underlying JoCaml, which supports the distributed implementation of OCaml components.In this paper, we support the distributability of the two models on theoretical grounds. For this, we investigate three refined variants of the π-calculus that can be understood as the essence of the two models. We show that neither of the three calculi is able to express a synchronization pattern that is known from the world of Petri nets and that was used by us as one criterion in a distributability hierarchy of process calculi. Moreover, we exhibit three encodings between the three calculi and prove that they each preserve the degree of distributability between source and target terms.

On the modeling and verification of the spread of fake news, algebraically

Abstract In recent years, one of the major issues concerning the study of online social network phenomena is related to the diffusion of misinformation, commonly known as fake news. In the literature, several mathematical tools are used to investigate both the identifying attributes of fake news and their spreading model. This work concentrates on the latter aspect and follows the lines of research inspired by the analysis of epidemic models. Its main contribution is the definition of a modeling framework based on process algebra for the explicit, formal representation of typical behavioral patterns of agents in social networks, and the use of a probabilistic verification framework based on modal logics and model checking for the quantitative analysis of the fake news spread.

Response time analysis of a manufacturing supply chain with performance evaluation process algebra

The supply and demand shocks brought on by the Covid-19 crisis are forcing manufacturers everywhere to reassess or even reorganise their supply chains. This paper proposes a general framework that can achieve fast compositional modelling with stochastic performance evaluation process algebra (PEPA) for supply chain systems. The key feature of such a framework is the PEPA-based quantitative analysis approach which includes a new method for calculating response time based on compositional PEPA models. The framework aims to provide an efficient modelling prototype for supply chain systems while supporting accurate response time-based quantitative analysis. To our knowledge, this is the first work using process algebra-based compositional modelling to quantitatively analyse supply chain systems.

Safety Verification of Driving Resource Occupancy Rules Based on Functional Language

Autonomous driving is a safety-critical system, and the occupancy of its environmental resources affects the safety of autonomous driving. In view of the lack of safety verification of environmental resource occupation rules in autonomous driving, this paper proposes a verification method of automatic driving model based on functional language through CSPM. Firstly, the modeling and verification framework of an autopilot model based on CSPM is given. Secondly, the process algebra definition of CSPM is given. Thirdly, the typical single loop environment model in automatic driving is abstracted, and the mapping method from automatic driving model to CSP is described in detail for the automatic driving environment and the typical collision, overtaking, lane change and other scenes involved. Finally, the autopilot model of the single loop is mapped to CSPM, and the application effect of this method is discussed by using FDR tool. Experiments show that this method can verify the safety of autonomous driving resources, thereby improving the reliability of the autonomous driving model.

Formal Modeling and Performance Evaluation for Hybrid Systems: A Probabilistic Hybrid Process Algebra-Based Approach

Probabilistic behavior is omnipresent in computer-controlled systems, in particular, so-called safety-critical hybrid systems, due to various reasons, like uncertain environments or fundamental properties of nature. In this paper, we extend the existing hybrid process algebra ACP[Formula: see text] with probability without sacrificing the nondeterministic choice operator. The existing approximate probabilistic bisimulation relation is fragile and not robust in the sense of being dependent on the deviation range of the transition probability. To overcome this defect, a novel approximate probabilistic bisimulation is proposed which is inspired by the idea of Probably Approximately Correct (PAC) by relaxing the constraints of transition probability deviation range. Traditional temporal logics, even probabilistic temporal logics, are expressive enough, but they are limited to producing only true or false responses, as they are still logics and not suitable for performance evaluation. To settle this problem, we present a new performance evaluation language that expands quantitative analysis from the value range of [Formula: see text] to real number to reason over probabilistic systems. After that, the corresponding algorithms for performance evaluation are given. Finally, an industrial example is given to demonstrate the effectiveness of our method.

The Classical-Quantum Dichotomy from the Perspective of the Process Algebra.

The classical-quantum dichotomy is analyzed from the perspective of the Process Algebra approach, which views fundamental phenomena through the lens of complex systems theory and Whitehead’s process theory. Broadly, the dichotomy can be framed in terms of differences in ontology (phenomena and their behavior) and differences in epistemology (theoretical languages used in their description). The Process Algebra posits a reality, generated by processes, whose fundamental characteristics include becoming, generativity, transience, locality, and contextuality. From this perspective, the classical-quantum dichotomy appears to be a false dichotomy—it arises because of stereotyped, strawman-like depictions of what it means to be classical or quantum. A more careful examination reveals that reality is unitary, that whether a system behaves in a quantum or classical manner depends upon its particularities, in particular, whether it is complex or not, and how information flows govern its dynamics.

A Formal Method for Description and Decision of Android Apps Behavior Based on Process Algebra

Android is the most popular mobile platform, and it has become a primary malware target. Existing behavior-based Android malware detection methods suffer from false positive and false negative problems, which lead to low detection accuracy. Formal theory is crucial in studying the behaviors of Android applications characterized by high concurrency, interaction, and mobility. However, existing formal methods mainly focus on specific issues and lack the essential abstraction and high-level description of application behavior. In this study, we propose a formal method for the description and decision of application behavior based on process algebra. First, we propose a formal method for describing application behavior at a component level using process algebra. By extending π-calculus theory, we establish the mapping relationship from the Android application to process algebra, and present the semantics and evolution rules of behavior based on process algebra. Second, we describe the behavior of four types of components in applications and characterize concurrent interactions of components using process algebra expressions. Third, we define the behavior equivalence and simulation mechanism for application behavior analysis and propose the decision rules based on weak simulation. Finally, we discuss a demonstration case, which includes malicious behavior, to demonstrate the feasibility and effectiveness of the proposed method. The results show that our method can accurately describe and analyze application behavior, which provides theoretical support for technologies and methods of behavior-based detection.

Compositional Equivalences Based on Open Pnets

Establishing equivalences between programs or system is crucial both for verifying correctness of programs, by establishing that two implementations are equivalent, and for justifying optimisations and program transformations, by establishing that a modified program is equivalent to the source one. There exist several equivalence relations for programs, and bisimulations are among the most versatile of these equivalences. Among bisimulation relations one distinguishes strong bisimulation, that requires that each action of a program is simulated by a single action of the equivalent program, a weak bisimulation that is a coarser relations, allowing some of the actions to be invisible or internal moves, and thus not simulated by the equivalent program. pNets is a generalisation of automata that includes parameters, and hierarchical composition. Open pNets are pNets with holes, i.e. placeholders inside the hierarchical structure that can be filled by subsystems. Reasoning on open pNets allows us to reason on open systems. Open pNets have a notion of synchronised actions generalizing the usual internal actions (e.g. τ of CCS, or i in Lotos). This article defines bisimulation relations for the comparison of systems specified as pNets. We first define a strong bisimulation for open pNets. In practice, as happens in process algebras, strong bisimulation is too strong, and we need to define some coarser relations, taking into account invisible or internal moves. We then define an equivalence relation similar to the classical weak bisimulation, and study its properties. Among these properties we are interested in compositionality: If two systems are proven equivalent they will be undistinguishable by their context, and they will also be undistinguishable when their holes are filled with equivalent systems. The article is illustrated with a transport protocol running example; it shows the characteristics of our formalism and our bisimulation relations.

Malliavin calculus for marked binomial processes and applications

We develop stochastic analysis tools for marked binomial processes (MBP) that are the discrete analogues of the marked Poisson processes. They include in particular: (i) the statement of a chaos decomposition for square-integrable functionals of MBP, (ii) the design of a tailor-made Malliavin calculus of variations, (iii) the statement of the analogues of Stroock’s, Clark’s and Mehler’s formulas. We provide our formalism with two applications: (App1) studying the (compound) Poisson approximation of MBP functional by combining it with the Chen-Stein method and (App2) solving an optimal hedging problem in the trinomial model.

Compositional Verification of Non-Blockingness with Prioritised Events

This paper addresses the verification of non-blockingness for modular discrete-event systems, i.e., discrete-event systems that are composed from component models. For such systems, the explicit construction of a monolithic representation turns out intractable for relevant applications, since such a construction in general is of exponential cost w.r.t. the number of components. One well established approach to circumvent the need for a monolithic representation for the verification task at hand is to alternate (a) the substitution of individual components by abstractions and (b) the composition of only a small number of strategically chosen components at a time. When successful, one ends up with a single moderately sized automaton which does not represent the overall behaviour in any detail but which does block if and only if the original modular system fails to be non-conflicting. This approach is referred to as compositional verification and originates from the field of process algebra with more recent adaptations to finite automata models. The main contribution of the present study is the development of a number of abstraction rules valid for compositional verification of non-conflictingness in the presence of global event priorities, i.e., where high priority events from one component possibly preempt events with lower priority of other components.

Formalization and Analysis of Ceph Using Process Algebra

Ceph is an object-based parallel distributed file system that provides excellent performance, reliability, and scalability. Additionally, Ceph provides its Cephx authentication system to authenticate users, so that it can identify users and realize authentication. In this paper, we first model the basic architecture of Ceph using process algebra CSP (Communicating Sequential Processes). With the help of the model checker PAT (Process Analysis Toolkit), we feed the constructed model to PAT and then verify several related properties, including Deadlock Freedom, Data Reachability, Data Write Integrity, Data Consistency and Authentication. The verification results show that the original model cannot cater to the Authentication property. Therefore, we formalize a new model of Ceph where Cephx is adopted. In the light of the new verification results, it can be found that Cephx satisfies all these properties.

Засоби забезпечення та засвідчення якості контекстно-залежної композиції семантичних веб-сервісів

Author’s Method for Adaptive Semantic Web Service dynamic composition is enriched with the algorithms for both its Context dedicated OWL-S-specification consistent using over its Life Cycle and Cyclic Dependencies at the function level solving with the Formalisms proposed of Knot-service, Proxy-service and Simplification – for sustain Quality implementing of Web Service being formed. Quality assurance for stakeholders is proposed through dynamic verification, in particular meeting the specified context and liveness, with the process Calculus of Context-aware Ambients. The algorithms proposed increase correspondence of Web Service being formed with Customers’ expectations and enable its sustain context-aware tailoring for unified support of both modern organizations’ variable and distributed Business Processes and some problem field Customers’ needs.

The Future of Modelling Languages in Industry – Why Practitioners Do Not Use Your Favourite Process Algebra

The Future of Modelling Languages in Industry – Why Practitioners Do Not Use Your Favourite Process Algebra

A process calculus for privacy-preserving protocols in location-based service systems

Location privacy-preserving mechanisms (LPPM) were introduced to protect users of location-based services (LBS) from the privacy threat of leaked personal data. These mechanisms alter the communication to the LBS in such a way that no malicious party can derive sensitive personal data. In the literature one can find many different LPPMs with varying privacy guarantees but so far no formal framework exists for comparing all of these mechanisms and their privacy guarantees. We propose the σ-calculus, which enables the modeling of LPPMs and location privacy guarantees. The calculus entails a process language, a property language, and a temporal-K-less-epistemic modal logic that enables the verification of location privacy properties on process models. The σ-calculus is a novel process calculus that is based on standard set operations that are computationally cheap, yet sufficient for modeling privacy violations in LBS communication. The calculus is the first formal framework to model and reason about a wide array of LPPMs. Furthermore, we present model checking algorithms that enable the automatic verification of location privacy properties. We evaluate the expressiveness of our process language by modeling a significant number of LPPMs from the literature and the expressiveness of our property language by describing a benchmark set of location privacy properties. Furthermore, we demonstrate the verification of a privacy property with an extended example of an LPPM algorithm designer. We developed the tool LP3Verif that implements our model checking algorithms. The open-source tool is written in Java and uses the SMT solver CVC4 as back end.

Knowledge Dynamics and Behavioural Equivalences in Multi-Agent Systems

We define a process calculus to describe multi-agent systems with timeouts for communication and mobility able to handle knowledge. The knowledge of an agent is represented as sets of trees whose nodes carry information; it is used to decide the interactions with other agents. The evolution of the system with exchanges of knowledge between agents is presented by the operational semantics, capturing the concurrent executions by a multiset of actions in a labelled transition system. Several results concerning the relationship between the agents and their knowledge are presented. We introduce and study some specific behavioural equivalences in multi-agent systems, including a knowledge equivalence able to distinguish two systems based on the interaction of the agents with their local knowledge.

Modeling of a Generic Edge Computing Application Design.

Edge computing applications leverage advances in edge computing along with the latest trends of convolutional neural networks in order to achieve ultra-low latency, high-speed processing, low-power consumptions scenarios, which are necessary for deploying real-time Internet of Things deployments efficiently. As the importance of such scenarios is growing by the day, we propose to undertake two different kind of models, such as an algebraic models, with a process algebra called ACP and a coding model with a modeling language called Promela. Both approaches have been used to build models considering an edge infrastructure with a cloud backup, which has been further extended with the addition of extra fog nodes, and after having applied the proper verification techniques, they have all been duly verified. Specifically, a generic edge computing design has been specified in an algebraic manner with ACP, being followed by its corresponding algebraic verification, whereas it has also been specified by means of Promela code, which has been verified by means of the model checker Spin.

Performance evaluation in stochastic process algebra dtsdPBC

Performance evaluation in stochastic process algebra dtsdPBC

Processes, Systems & Tests: Defining Contextual Equivalences

In this position paper, we would like to offer and defend a new template to study equivalences between programs -- in the particular framework of process algebras for concurrent computation.We believe that our layered model of development will clarify the distinction that is too often left implicit between the tasks and duties of the programmer and of the tester. It will also enlighten pre-existing issues that have been running across process algebras as diverse as the calculus of communicating systems, the $\pi$-calculus -- also in its distributed version -- or mobile ambients.Our distinction starts by subdividing the notion of process itself in three conceptually separated entities, that we call \emph{Processes}, \emph{Systems} and \emph{Tests}. While the role of what can be observed and the subtleties in the definitions of congruences have been intensively studied, the fact that \emph{not every process can be tested}, and that \emph{the tester should have access to a different set of tools than the programmer} is curiously left out, or at least not often formally discussed.We argue that this blind spot comes from the under-specification of contexts -- environments in which comparisons takes place -- that play multiple distinct roles but supposedly always \enquote{stay the same}.We illustrate our statement with a simple Java example, the \enquote{usual} concurrent languages, but also back it up with $\lambda$-calculus and existing implementations of concurrent languages as well.

Decomposing Monolithic Processes in a Process Algebra with Multi-actions

A monolithic process is a single recursive equation with data parameters, which only uses non-determinism, action prefixing, and recursion. We present a technique that decomposes such a monolithic process into multiple processes where each process defines behaviour for a subset of the parameters of the monolithic process. For this decomposition we can show that a composition of these processes is strongly bisimilar to the monolithic process under a suitable synchronisation context. Minimising the resulting processes before determining their composition can be used to derive a state space that is smaller than the one obtained by a monolithic exploration. We apply the decomposition technique to several specifications to show that this works in practice. Finally, we prove that state invariants can be used to further improve the effectiveness of this decomposition technique.