: A distributed real-time logic language

This paper presents a new language that integrates the real-time and distributed paradigms within the framework of a concurrent logic language. Concurrent logic languages (CLLs) are capable of expressing concurrence, communication and nondeterminism in a natural way. That is, the intrinsic parallel semantics of the concurrent logic languages makes them well-suited for distributed programming. The proposed language is particularly suitable for loosely coupled systems and it contains mechanisms for distributed and real-time process control. A new execution model for concurrent logic languages is presented, which enables efficient distributed execution and real-time control. The model is introduced by giving an operational semantics for the language and the new model's implementation is discussed, including the definition of a new abstract machine and its implementation on a network of Unix workstations. Although the sequential core is not optimized, some previous results are discussed, showing the feasibility of the language's execution model for distributed real-time systems. The language is currently being used as the kernel language for a distributed simulation and validation tool for communication protocols.     

Temporal Semantics for Concurrent M M

Concurrent is a programming language based on the notion of concurrent, communicating objects, where each object directly executes a specification given in temporal logic, and communicates with other objects using asynchronous broadcast message-passing. Thus, Concurrent represents a combination of the direct execution of temporal specifications, together with a novel model of concurrent computation. In contrast to the notions of predicates as processes and stream parallelism seen in concurrent logic languages, Concurrent represents a more coarse-grained approach, where an object consists of a set of logical rules and communication is achieved by the evaluation of certain types of predicate. Representing concurrent systems as groups of such objects provides a powerful tool for modelling complex reactive systems. In order to reason about the behaviour of Concurrent systems, we requir a suitable semantics. Being based upon executable temporal logic, objects in isolation have an intuitive semantics. However, the addition of both operational constraints upon the object's execution and global constraints provided by the asynchronous model of concurrency and communication, complicates the overall semantics of networks of objects. It is this, more complex, semantics that we address here, where temporal semantics for varieties of Concurrent are provided.     

LET模型的时间语义编程语言

嵌入式实时系统的正确性不仅取决于计算结果的正确性,更取决于产生结果时间的正确性.然而软件不确定的并发执行带来系统时间行为不可预测问题,使得验证复杂度升高,成本增加,为此实时系统领域提出了许多实时编程语言来提高系统的时间可预测性.LET(logical execution time)模型结合了同步模型ZET(zero e...     

A lingua franca for concurrent logic programming

Two of the more important concurrent logic programming languages with nonflat guards are GHC and Parlog. They balance the requirements of having clean semantics and providing good control facilities rather differently, and their respective merits are compared and contrasted. Since concurrent logic programming would benefit from both, but neither language is able to express all the programs expressible in the other language, a lingua franca of these languages is defined and justified. A method is given for translating GHC and Parlog to and from it. The method preserves the arities and execution conditions of each clause. It enables a lingua franca implementation to support both languages transparently, and to provide a simple concurrent logic programming language suitable for programming in its own right     

A formal semantics for debugging synchronous message passing-based concurrent programs

In this paper, we propose a semantic framework to debug synchronous message passing-based con- current programs, which are increasingly useful as parallel computing and distributed systems become more and more pervasive. We first design a concurrent programming language model to uniformly represent exist- ing concurrent programming languages. Compared to sequential programming languages, this model contains communication statements, i.e., sending and receiving statements, and a concurrent structure to represent com- munication and concurrency. We then propose a debugging process consisting of a tracing and a locating procedure. The tracing procedure re-executes a program with a failed test case and uses specially designed data structures to collect useful execution information for locating bugs. We provide for the tracing procedure a struc- tural operational semantics to represent synchronous communication and concurrency. The locating procedure backward locates the ill-designed statement by using information obtained in the tracing procedure, generates a fix equation, and tries to fix the bug by solving the fix equation. We also propose a structural operational semantics for the locating procedure. We supply two examples to test our proposed operational semantics.     

A Proposal for a Distributed Model of GKS Based on Prolog

The Graphical Kernel System GKS is so well established as a standard for graphics programming that quite a number of models for multiprocessor and distributed environments have already been suggested. It is therefore necessary to consider new languages and methodologies capable of supporting its distributed implementation. In this context, clausal logic languages provide suitable means for describing the system in a declarative form and, moreover, ensure the applicability of meta-programming techniques for specifying the semantics of implementation. The Prolog language, extended with communication and modularization structures required by the distributed programming, is thus here considered as a feasible means for establishing a model of GKS organized in functional modules which could be supported by different processors. For such a model a two-level implementation scheme is outlined and a reconfiguration and personalization methodology is suggested.     

Early experience with the Visual Programmer's WorkBench

The Visual Programmer's WorkBench (VPW) addresses the rapid synthesis and customization of environments for the specification, analysis, and execution of visual programs. The goal of VPW is to enable the easy creation of environments for visual languages. The design of VPW and experience using it to generate a distributed programming environment for a concurrent visual language are described. A visual programming environment for the PetriFSA language generated with VPW is outlined. An overview is provided of the language definition model and its relation to the logical architecture of VPW. Details are given of the language specifications used in VPW, and its application in defining the PetriFSA language. A language-based environment for a specific visual language is generated in VPW from a specification of the syntactic structure, the abstract structure, the static semantics, and the dynamic semantics of the language. VPW is built around a model of distributed processing based on a shared distributed memory. This framework is used in defining the architecture of the environment and for the execution model of visual languages     

A unified formal basis for the CASE tools system

XYZ system is a CASE tools system based on a temporal logic language XYZ/E which can represent every essential feature of conventional HLL's (sequential or concurrent), specifications of different levels, production rules, operational semantics of graphic languages in a uniform framework. With this formal language as the common basis, all the CASE tools including various kinds of graphic tools for distributed process, concurrent programs with phased memory and sequential programs, tools for verification, rapid-prototyping, language transformation, and module management can be connected freely to form more sophisticated and integrated systems.     

可更新Datalog的分布式时态逻辑扩展及应用

针对现有的分布式逻辑语言缺乏完整时态表达力等问题,将分布式时态逻辑谓词引入Datalog规则,提出TU-Datalog语言。该语言通过融入U-Datalog的非即时性更新语义,形成完全声明式具有强大时态表达力的逻辑编程语言和环境。通过扩展U-Datalog逻辑固定点语义,提出TU-Datalog语言的固定点时态演化规则,并对该语言的语法、语义、评价算法进行了研究,最后对该语言的应用做了说明和示例。     

消息传递的MSVL通信机制及其实现

建模,仿真和验证语言（MSVL）是一种时序逻辑编程语言,它是投影时序逻辑（PTL）的可执行子集.MSVL和PTL可用于并发系统的建模和性质验证.然而,MSVL缺少一种消息传递的通信机制,这种机制对于并发分布式系统的建模和验证至关重要.本文说明了如何在MSVL中开发和实现合适的机制来对分布式系统进行建模和验证.该机制首先定义了通道结构,对通信语句和进程结构进行形式化描述,接着介绍了这些通信语句的实现机制.最后,提供了一个关于电子合同签名协议的建模和验证实例,说明消息传递在MSVL中的工作原理.     

Relating state-based and process-based concurrency through linear logic (full-version)

This paper has the purpose of reviewing some of the established relationships between logic and concurrency, and of exploring new ones.Concurrent and distributed systems are notoriously hard to get right. Therefore, following an approach that has proved highly beneficial for sequential programs, much effort has been invested in tracing the foundations of concurrency in logic. The starting points of such investigations have been various idealized languages of concurrent and distributed programming, in particular the well established state-transformation model inspired by Petri nets and multiset rewriting, and the prolific process-based models such as the π-calculus and other process algebras. In nearly all cases, the target of these investigations has been linear logic, a formal language that supports a view of formulas as consumable resources. In the first part of this paper, we review some of these interpretations of concurrent languages into linear logic and observe that, possibly modulo duality, they invariably target a small semantic fragment of linear logic that we call LV^obs.In the second part of the paper, we propose a new approach to understanding concurrent and distributed programming as a manifestation of logic, which yields a language that merges those two main paradigms of concurrency. Specifically, we present a new semantics for multiset rewriting founded on an alternative view of linear logic and specifically LV^obs. The resulting interpretation is extended with a majority of linear connectives into the language of ω-multisets. This interpretation drops the distinction between multiset elements and rewrite rules, and considerably enriches the expressive power of standard multiset rewriting with embedded rules, choice, replication, and more. Derivations are now primarily viewed as open objects, and are closed only to examine intermediate rewriting states. The resulting language can also be interpreted as a process algebra. For example, a simple translation maps process constructors of the asynchronous π-calculus to rewrite operators. The language of ω-multisets forms the basis for the security protocol specification language MSR 3. With relations to both multiset rewriting and process algebra, it supports specifications that are process-based, state-based, or of a mixed nature, with the potential of combining verification techniques from both worlds. Additionally, its logical underpinning makes it an ideal common ground for systematically comparing protocol specification languages.     

Performance of multi-tasking and synchronization mechanisms in the programming language SR

High-level language primitives for concurrent programming exist in languages such as Ada and Modula-2. However, each of these languages provides only a single means for specifying multitasking and synchronization, essential in the implementation of concurrent systems. The SR language provides several mechanisms for specifying multi-tasking and synchronization, so it can be used to explore the performance of various communication techniques. This paper presents performance results for SR's multi-tasking and synchronization mechanisms and discusses the effects of the generated code, the run-time support and the hardware on these results. These results are compared with those for similar mechanisms in other languages, leading to some general conclusions about the performance of process communication primitives. These performance results can be used by programmers to make design choices that allow systems programs written in high-level languages to meet real-time performance specifications.     

A common intermediate language and its use in partitioning concurrent declarative programs

The plethora of concurrent declarative language families, each with subtly different semantics, makes the design and implementation of static analyses for these languages a demanding task. However, many of the languages share underlying structure, and if this structure can be exploited, static analysis techniques can be shared across language families. These techniques can thus provide a common kernel for the implementation of quality compilers for this entire language class. The purpose of this paper is to exploit the similarities of non-strict functional and concurrent logic languages in the design of a common intermediate language (CIL). The CIL is introduced incrementally, giving at each step the rationale for its extension. As an application, we present, in CIL form, some state-of-the-art static partitioning algorithms from the literature. This allows us to “uncover” the relative advantages and disadvantages of the analyses, and determine promising directions for improving static partitioning.     

Formalizing the specification and execution of workflows using the event calculus

The event calculus is a logic programming formalism for representing events and their effects especially in database applications. This paper proposes the event calculus as a logic-based methodology for the specification and execution of workflows. It is shown that the control flow graph of a workflow specification can be expressed as a set of logical formulas and the event calculus can be used to specify the role of a workflow manager through a set of rules for the execution dependencies of activities. The proposed framework for a workflow manager maintains a history of events to control the execution of activities. The events are instructions to the workflow manager to coordinate the execution of activities. Based on the already occurred events, the workflow manager triggers new events to schedule new activities in accordance with the control flow graph of the workflow. The net effect is an alternative approach for defining a workflow engine whose operational semantics is naturally integrated with the operational semantics of a deductive database. Within this framework it is possible to model sequential and concurrent activities with or without synchronization. It is also possible to model agent assignment and execution of concurrent workflow instances. The paper, thus, contributes a logical perspective to the task of developing formalization for the workflow management systems.     

动态优先系统及其应用

优先关系是并发系统控制的重要手段,常用于解决并发系统设计中的冲突问题.在有界P/T系统的基础上提出一种动态优先系统,并分别给出它们的交错语义与真并发语义.动态优先系统既可以作为并发与分布式系统的建模工具,也可以作为定义程序设计语言中优先算子的语义基础.最后,基于动态优先系统的概念,为Occam语言扩充了一种动态优先选择算子.     

Communication infrastructure in distributed scheduling

The emergence of distributed artificial intelligent (DAI) introduced a new approach to solve scheduling problems by a set of scheduling systems that interact with each other in the problem-solving process. In this paper, we describe a communication infrastructure to handle connection and communication between distributed Internet scheduling systems for distributed applications. First, we present an agent model of distributed scheduling systems where agents can communicate and coordinate activities with each other via an agent communication language. Then, we define the syntax and semantics for the agent communication languages, and negotiation mechanism. Following that, we discuss the design and development of the prototype for the multi-agent scheduling systems. We conclude with a discussion of communication issues for heterogeneous agent-based scheduling systems to solve distributed scheduling problems.     

SystemJ: A GALS language for system level design

In this paper we present the syntax, semantics, and compilation of a new system-level programming language called SystemJ. SystemJ is a multiclock language supporting the Globally Asynchronous Locally Synchronous (GALS) model of computation. The synchronous reactive (SR) model is used for synchronous parts of the modelled system, and those parts, which represent individual clock-domains, are coupled asynchronously each to the other on the top-level of system design. SystemJ is based on Java language, which is used to describe “instantaneous” data transformations. Hence, SystemJ is well suited for both software-based embedded and distributed systems. SystemJ offers effective modelling of (1) data transformations through the power of Java, (2) control and synchronous concurrency through the SR paradigm and (3) asynchronous concurrency through clock domains and rendezvous. The language is based on semantics that is amenable to efficient code generation and partial automatic verification. The SystemJ micro-step semantics provide asynchronous and synchronous extensions over the semantics of other SR languages such as Esterel and provide an ideal platform for efficient software implementation.     

DisCComp – A Formal Model for Distributed Concurrent Components

Most large-scaled software systems are structured in distributed components to manage complexity and have to cope with concurrent executed threads. System decomposition and concurrent flow of execution are orthogonal. A sound semantic model that is powerful enough to handle distributed concurrent components but also realistic enough to provide a foundation for component technologies actually in use is still missing. Therefore, the paper introduces such an operational semantics for distributed concurrent component-based systems. Based on this formal model, UML-based modeling techniques are introduced. Tool support for modeling, code generation, and system execution is provided.