Rule-based systems formalized within a software architectural style

This article considers the utilization of architectural styles in the formal design of knowledge-based systems. The formal model of a style is an approach to systems modeling that allows software developers to understand and prove properties about the system design in terms of its components, connectors, configurations, and constraints. This allows commonality of design to be easily understood and captured, leading to a better understanding of the role that an architectural abstraction would have in another complex system, embedded context, or system integration. In this article, a formal rule-based architectural style is presented in detail using the Z notation. The benefits of depicting the rule-based system as an architectural style include reusability, understandability, and the allowance for formal software analysis and integration techniques. The ability to define the rule-based architectural style in this way, illustrates the power, clarity, and flexibility of this specification form over traditional formal specification approaches. In addition, it extends current verification approaches for knowledge-based systems beyond the knowledge base only.     

Modeling and enforcing invariants of dynamic software architectures

In this paper, we propose an “end-to-end” approach that supports dynamic reconfiguration of software architectures taking advantage of graphical modeling, formal methods and aspect-oriented programming. There are three ingredients of the proposal. The specification end of the solution is covered by a new UML profile enabling to specify the desired architectural style (model), its invariants and the intended reconfiguration operations. In order to verify the consistency of the model and the preservation of the invariants after every reconfiguration, we automatically generate formal specifications in Z notation from the defined model. At the runtime enforcing end of the solution, we propose to encode the enforcement logic as aspect in the AspectJ language. The third important ingredient that makes our approach end-to-end is the automatic translation of formal specifications into aspect-based enforcement code.     

RELOAD extension for data discovery and transfer in data-centric publish–subscribe environments

Data-Centric Publish–Subscribe (DCPS) is an architectural and communication paradigm where applications exchange data-content through a common data-space using publish-subscribe interactions. Due to its focus on data-content, DCPS is especially suitable for deploying IoT systems. However, some problems must be solved to support large deployments. In this paper we define a novel extension to the IETF REsource LOcation And Discovery (RELOAD) protocol specification for providing content discovery and transfer in big scale IoT deployments. We have conducted a set of experiments over multiple simulated networks of 500 to 10,000 nodes that demonstrate the viability, scalability, and robustness of our proposal.     

高性能发布／订阅系统接口服务的设计与应用

发布／订阅模型因其异步、多点通信,松耦合和易扩展的特点,被广泛应用于分布式环境中。本文在详细研究国内外发布／订阅系统现状的基础上,结合物联网应用环境,分析其中存在的问题和不足,针对主题组织形式、对复杂网络环境的适应以及系统整体性能提升等方面提出了改进措施,并对改进前后的系统性能进行了分析比较,旨在解决发布／订阅系统实用化过程中遇到的一系列问题,提供一种可应用在复杂网络环境中的高性能发布／订阅系统接口服务。     

The Real-Time Process Algebra (RTPA)

The real-time process algebra (RTPA) is a set of new mathematical notations for formally describing system architectures, and static and dynamic behaviors. It is recognized that the specification of software behaviors is a three-dimensional problem known as: (i) mathematical operations, (ii) event/process timing, and (iii) memory manipulations. Conventional formal methods in software engineering were designed to describe the 1-D (type (i)) or 2-D (types (i) and (iii)) static behaviors of software systems via logic, set and type theories. However, they are inadequate to address the 3-D problems in real-time systems. A new notation system that is capable to describe and specify the 3-D real-time behaviors, the real-time process algebra (RTPA), is developed in this paper to meet the fundamental requirements in software engineering.RTPA is designed as a coherent software engineering notation system and a formal engineering method for addressing the 3-D problems in software system specification, refinement, and implementation, particularly for real-time and embedded systems. In this paper, the RTPA meta-processes, algebraic relations, system architectural notations, and a set of fundamental primary and abstract data types are described. On the basis of the RTPA notations, a system specification method and a refinement scheme of RTPA are developed. Then, a case study on a telephone switching system is provided, which demonstrates the expressive power of RTPA on formal specification of both software system architectures and behaviors. RTPA elicits and models 32 algebraic notations, which are the common core of existing formal methods and modern programming languages. The extremely small set of formal notations has been proven sufficient for modeling and specifying real-time systems, their architecture, and static/dynamic behaviors in real-world software engineering environment.     

基于内容的发布/订阅拓扑模型设计和自配置协议研究

拓扑结构和自配置特性是实现大规模基于内容的发布/订阅系统的关键问题之一,决定了系统的可扩展性。为了提高发布/订阅系统性能,引入了空间划分的概念,设计了一个具有空间划分的层次拓扑模型。针对节点或者链路失效所带来的网络分割问题,本文在静态拓扑模型的基础上提出了一个自配置协议,提高了系统的可靠性和扩展性。     

An object based algebra for specifying a fault tolerant software architecture

In this paper we present an algebra of actors extended with mechanisms to model crash failures and their detection. We show how this extended algebra of actors can be successfully used to specify distributed software architectures. The main components of a software architecture can be specified following an object-oriented style and then they can be composed using asynchronous message passing or more complex interaction patterns. This formal specification can be used to show that several requirements of a software system are satisfied at the architectural level despite failures. We illustrate this process by means of a case study: the specification of a software architecture for intelligent agents which supports a fault tolerant anonymous interaction protocol.     

An MDE-based method for bridging different design notations

Different communities have developed plenty of design notations for software engineering in support of practical (via UML) and rigorous (via formal methods) approaches. Hence the problem of bridging these notations rises. Model-driven engineering (MDE) is a new paradigm in software engineering, which treats models and model transformations as first class citizens. Furthermore, it is seen as a promising method for bridging heterogeneous platforms. In this paper, we provide an MDE-based approach to build bridges between informal, semi-formal and formal notations: Firstly, different notations are viewed as different domain specification languages (DSLs) and introduced into MDE, especially into the ATLAS Model Management Architecture (AMMA) platform, by metamodeling. Then, ATL transformation rules are built for semantics mapping. At last, TCS-based model-to-text syntax rules are developed, allowing one to map models to programs. Consequently, different design notations in both graphical style and grammatical style are bridged. A case study of bridging OMG SysML™ to LOTOS is also illustrated showing the validity and practicability of our approach.     

一种实时系统软件体系结构风格:NewRob

该文分析了现有的软件体系结构风格描述语言的特点,并结合嵌入式实时系统的领域特征,提出了一个面向嵌入式实时系统的软件体系结构风格:NewRob。NewRob所生成的一个基本说明书,由一个同步控制任务组成,它负责将系统作为包含各类异步组件的集合,进行动态重构。控制任务通过对各组成元件逐级细化、分解,得到进化后的低级控制任务,每个低级任务也都管理一个新的组件集合。采用时序逻辑描述和验证不同抽象级别的软件体系结构的一致性。     

Translation of Z specifications to executable code: Application to the database domain

ContextIt is well-known that the use of formal methods in the software development process results in high-quality software products. Having specified the software requirements in a formal notation, the question is how they can be transformed into an implementation. There is typically a mismatch between the specification and the implementation, known as the specification-implementation gap.ObjectiveThis paper introduces a set of translation functions to fill the specification-implementation gap in the domain of database applications. We only present the formal definition, not the implementation, of the translation functions.MethodWe chose Z, SQL and Delphi languages to illustrate our methodology. Because the mathematical foundation of Z has many properties in common with SQL, the translation functions from Z to SQL are derived easily. For the translation of Z to Delphi, we extend Delphi libraries to support Z mathematical structures such as sets and tuples. Then, based on these libraries, we derive the translation functions from Z to Delphi. Therefore, we establish a formal relationship between Z specifications and Delphi/SQL code. To prove the soundness of the translation from a Z abstract schema to the Delphi/SQL code, we define a Z design-level schema. We investigate the consistency of the Z abstract schema with the Z design-level schema by using Z refinement rules. Then, by the use of the laws of Morgan refinement calculus, we prove that the Delphi/SQL code refines the Z design-level schema.ResultsThe proposed approach can be used to build the correct prototype of a database application from its specification. This prototype can be evolved, or may be used to validate the software requirements specification against user requirements.ConclusionTherefore, the work presented in this paper reduces the overall cost of the development of database applications because early validation reveals requirement errors sooner in the software development cycle.     

基于中间件的动态重配置容错对象管理框架

该文从容错QoS角度出发,为现有的基于中间件的容错对象管理框架增加自适应特性．首先把动态童配置定义成容错属性集（及其实现）、计算环境和资源变化描述、动态调整算法三者之间的互动关系,然后采用反射模型和发布／订阅模型建立了一个动态重配置管理框架,可以使系统在发现计算环境的变化、定制动态调整算法等多方面得到有力的支持,为系统有效实施动态重配置奠定了基础．     

Describing software architecture styles using graph grammars

We believe that software architectures should provide an appropriate basis for the proof of properties of large software. This goal can be achieved through a clearcut separation between computation and communication and a formal definition of the interactions between individual components. We present a formalism for the definition of software architectures in terms of graphs. Nodes represent the individual agents and edges define their interconnection. Individual agents can communicate only along the links specified by the architecture. The dynamic evolution of an architecture is defined independently by a “coordinator”. An architecture style is a class of architectures specified by a graph grammar. The class characterizes a set of architectures sharing a common communication pattern. The rules of the coordinator are statically checked to ensure that they preserve the constraints imposed by the architecture style     

The Smart Architect: Scalable Ontology-Based Modeling of Ancient Chinese Architectures

The smart architect is an innovative intelligent modeling system that can automatically generate architectures in the ancient Chinese architectural style using an ontology-based approach. Our approach aims to implement an architecture modeling system that can identify different elements and styles in a variety of buildings. It should also be able to generate numerous architectures of similar structures or styles based on the semantic knowledge extracted from existing buildings.     

Modelling Dynamic Software Architectures using Typed Graph Grammars

Several recent research efforts have focused on the dynamic aspects of software architectures providing suitable models and techniques for handling the run-time modification of the structure of a system. A large number of heterogeneous proposals for addressing dynamic architectures at many different levels of abstraction have been provided, such as programmable, ad-hoc, self-healing and self-repairing among others. It is then important to have a clear picture of the relations among these proposals by formulating them into a uniform framework and contrasting the different verification aspects that can be reasonably addressed by each proposal. Our work is a contribution in this line. In particular, we map several notions of dynamicity into the same formal framework in order to distill the similarities and differences among them. As a result we explain different styles of architectural dynamisms in term of graph grammars and get some better insights on the kinds of formal properties that can be naturally associated to such different specification styles. We take a simple automotive scenario as a running example to illustrate main ideas.     

大规模发布／订阅系统中的可靠性模型

大多数Internet上的大规模发布/订阅系统,其覆盖网络是不可靠的,系统的可靠性和处理故障的能力是一个挑战性的问题.基于轨迹序列和线性时态逻辑定义系统的可靠性条件,是路由算法可靠性分析的基础.设计了崩溃/恢复模式的路由协议,维持一致的、共享的系统状态,有效地处理具有局部性、临时性的路由器故障和链路故障.