Adopting Architectural Event Modules for Modular Coordination of Multiple Applications

Nowadays, large-scale software systems consist of multiple applications, which interact with each other to fulfill desired system-level requirements. It is usually required to coordinate the interactions of the constituent applications to ensure that the system-level requirements are fulfilled. In this paper, we outline a set of requirements that must be fulfilled to facilitate the modular composition of multiple applications. We introduce the concept of architectural event modules, which are abstractions to represent constituent applications and their coordination logic in a modular and uniform way. We explain the implementation of this concept in the EventReactor language, and define their formal semantics in processing events using the UPPAAL toolset. We illustrate the suitability of architectural event modules in achieving modularity and loose coupling in the composition of multiple applications by means of a case study in the domain of energy-efficient computing

An Overview of Event-based Facades for Modular Composition and Coordination of Multiple Applications

Complex software systems are usually developed as systems of systems (SoS’s) in which multiple constituent applications are composed and coordinated to fulfill desired system-level requirements. The constituent applications must be augmented with suitable coordination-specific interfaces, through which they can participate in coordinated interactions. Such interfaces as well as coordination rules have a crosscutting nature. Therefore, to increase the reusability of the applications and to increase the comprehensibility of SoS’s, suitable mechanisms are required to modularize the coordination rules and interfaces from the constituent applications. We introduce a new abstraction named as architectural event modules (AEMs), which facilitate defining constituent applications and desired coordination rules as modules of SoS’s. AEMs augment the constituent applications with event-based facades to let them participate in coordinated interactions. We introduce the EventArch language in which the concept of AEMs is implemented, and illustrate its suitability using a case study

An Overview of Language Support for Modular Event-driven Programming

Nowadays, event processing is becoming the backbone of many applications. Therefore, it is necessary to provide suitable abstractions to properly modularize the concerns that appear in event-driven applications. We identify four categories of languages that support event-driven programming, and identify their shortcomings in achieving modularity in the implementation of applications. We propose gummy modules and their implementation in the GummyJ language as a solution. Gummy modules have well-defined event-based interfaces, and can have a primitive or a composite structure. Composite gummy modules are means to group a set of correlated event processing concerns and restrict the visibility of events among them. We provide an example usage of gummy modules, and discuss their event processing semantics

Hermeneutics framework: integration of design rationale and optimizing software modules

To tackle the evolution challenges of adaptive systems, this paper argues on the necessity of hermeneutic approaches that help to avoid too early elimination of design alternatives. This visionary paper proposes the Hermeneutics Framework, which computationally integrates a design rationale management system, an auto-adaptive control system and a reflective and modular event-driven language runtime together. The Hermeneutics Framework is, among others, suitable for implementing dynamic adaptive software systems that undergo intensive evolution cycles

Aspect structure of compilers

Compilers are among the most widely-studied pieces of software; and, modularizing these valuable artifacts is a recurring theme in research. However, modularization of cross-cutting concerns in compilers is not yet well explored. Even today, implementation of one compiler concern scatters across and tangles with the implementation of several other concerns, thereby leading to a mismatch between different compiler modules and the operations they represent. Essentially, current compiler implementations fail to explicitly identify the control dependencies of different phases, and separately characterize the actions to execute during those phases. As a result, information about their program-execution path remains non-intuitive: it stays hidden within the program structure and cuts-across several phase implementations. Consequently, this makes compiler designs and artifacts difficult to comprehend, maintain and reuse. Such limitations occur primarily as a result of the inability of mainstream object-oriented languages, such as Java, to organize the cross-cutting concerns into clean modular units. This thesis demonstrates how such modularity-issues in compilers can be addressed with the help of a relatively new, yet powerful programming paradigm called aspect-oriented programming

Design, Semantics and Implementation of the Ptolemy Programming Language: A Language with Quantified Typed Events

Implicit invocation (II) and aspect-oriented (AO) languages provide software designers with related but distinct mechanisms and strategies for decomposing programs into modules and composing modules into systems. II languages have explicitly announced events that run registered observer methods. AO languages have implicitly announced events that run method-like but more powerful advice. A limitation of II languages is their inability to refer to a large set of events succinctly. They also lack the expressive power of AO advice. Limitations of AO languages include potentially fragile dependence on syntactic structure that may hurt maintainability, and limits on the available set of implicit events and the reflective contextual information available. Quantified, typed events, as implemented in our language Ptolemy, solve all these problems. This paper describes Ptolemy and explores its advantages relative to both II and AO languages

An Expressive Stateful Aspect Language

Abstract Stateful aspects can react to a program execution; they support modular implementations of several crosscutting concerns like error detection, security, event handling, and debugging. However, most proposed stateful aspect languages have specifically been tailored to address a particular concern. Indeed, most of these languages differ in their pattern languages and semantics. As a consequence, developers need to tweak aspect definitions in contortive ways or create new specialized stateful aspect languages altogether if their specific needs are not supported. In this paper, we describe ESA, an expressive stateful aspect language, in which the pattern language is Turing-complete and patterns themselves are reusable, composable first-class values. In addition, the core semantic elements of every aspect in ESA is open to customization. We describe ESA in a typed functional language. We use this description to develop a concrete and practical implementation of ESA for JavaScript. With this implementation, we illustrate the expressiveness of ESA in action with examples of diverse scenarios and expressing semantics of existing stateful aspect languages

Dynamic Reconfiguration with Virtual Services

We present a new architecture (virtual services) and accompanying implementation for dynamically adapting and reconfiguring the behavior of network services. Virtual services are a compositional middleware system that transparently interposes itself between a service and a client, overlaying new functionality with configurations of modules organized into processing chains. Virtual services allow programmers and system administrators to extend, modify, and reconfigure dynamically the behavior of existing services for which source code, object code, and administrative control are not available. Virtual service module processing chains are instantiated on a per connection or invocation basis, thereby enabling the reconfiguration of individual connections to a service without affecting other connections to the same service. To validate our architecture, we have implemented a virtual services software development toolkit and middleware server. Our experiments demonstrate that virtual services can modularize concerns that cut across network services. We show that we can reconfigure and enhance the security properties of services implemented as either TCP client-server systems, such as an HTTP server, or as remotely invocable objects, such as a Web service. We demonstrate that virtual services can reconfigure the following security properties and abilities: authentication, access control, secrecy/encryption, connection monitoring, security breach detection, adaptive response to security breaches, concurrent and dynamically mutable implementation of multiple security policies for different clients