23,406 research outputs found

    Pattern Reification as the Basis for Description-Driven Systems

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    One of the main factors driving object-oriented software development for information systems is the requirement for systems to be tolerant to change. To address this issue in designing systems, this paper proposes a pattern-based, object-oriented, description-driven system (DDS) architecture as an extension to the standard UML four-layer meta-model. A DDS architecture is proposed in which aspects of both static and dynamic systems behavior can be captured via descriptive models and meta-models. The proposed architecture embodies four main elements - firstly, the adoption of a multi-layered meta-modeling architecture and reflective meta-level architecture, secondly the identification of four data modeling relationships that can be made explicit such that they can be modified dynamically, thirdly the identification of five design patterns which have emerged from practice and have proved essential in providing reusable building blocks for data management, and fourthly the encoding of the structural properties of the five design patterns by means of one fundamental pattern, the Graph pattern. A practical example of this philosophy, the CRISTAL project, is used to demonstrate the use of description-driven data objects to handle system evolution.Comment: 20 pages, 10 figure

    The SATIN component system - a metamodel for engineering adaptable mobile systems

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    Mobile computing devices, such as personal digital assistants and mobile phones, are becoming increasingly popular, smaller, and more capable. We argue that mobile systems should be able to adapt to changing requirements and execution environments. Adaptation requires the ability-to reconfigure the deployed code base on a mobile device. Such reconfiguration is considerably simplified if mobile applications are component-oriented rather than monolithic blocks of code. We present the SATIN (system adaptation targeting integrated networks) component metamodel, a lightweight local component metamodel that offers the flexible use of logical mobility primitives to reconfigure the software system by dynamically transferring code. The metamodel is implemented in the SATIN middleware system, a component-based mobile computing middleware that uses the mobility primitives defined in the metamodel to reconfigure both itself and applications that it hosts. We demonstrate the suitability of SATIN in terms of lightweightedness, flexibility, and reusability for the creation of adaptable mobile systems by using it to implement, port, and evaluate a number of existing and new applications, including an active network platform developed for satellite communication at the European space agency. These applications exhibit different aspects of adaptation and demonstrate the flexibility of the approach and the advantages gaine

    Composing Software from Multiple Concerns: A Model and Composition Anomalies

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    Constructing software from components is considered to be a key requirement for managing the complexity of software. Separation of concerns makes only sense if the realizations of these concerns can be composed together effectively into a working program. Various publications have shown that composability of software is far from trivial and fails when components express complex behavior such as constraints, synchronization and history-sensitiveness. We believe that to address the composability problems, we need to understand and define the situations where composition fails. To this aim, in this paper we (a) introduce a general model of multi-dimensional concern composition, and (b) define so-called composition anomalies

    An Analysis of Composability and Composition Anomalies

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    The separation of concerns principle aims at decomposing a given design problem into concerns that are mapped to multiple independent software modules. The application of this principle eases the composition of the concerns and as such supports composability. Unfortunately, a clean separation (and composition of concerns) at the design level does not always imply the composability of the concerns at the implementation level. The composability might be reduced due to limitations of the implementation abstractions and composition mechanisms. The paper introduces the notion of composition anomaly to describe a general set of unexpected composition problems that arise when mapping design concerns to implementation concerns. To distinguish composition anomalies from other composition problems the requirements for composability at the design level is provided. The ideas are illustrated for a distributed newsgroup system

    Fine Grained Component Engineering of Adaptive Overlays: Experiences and Perspectives

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    Recent years have seen significant research being carried out into peer-to-peer (P2P) systems. This work has focused on the styles and applications of P2P computing, from grid computation to content distribution; however, little investigation has been performed into how these systems are built. Component based engineering is an approach that has seen successful deployment in the field of middleware development; functionality is encapsulated in ‘building blocks’ that can be dynamically plugged together to form complete systems. This allows efficient, flexible and adaptable systems to be built with lower overhead and development complexity. This paper presents an investigation into the potential of using component based engineering in the design and construction of peer-to-peer overlays. It is highlighted that the quality of these properties is dictated by the component architecture used to implement the system. Three reusable decomposition architectures are designed and evaluated using Chord and Pastry case studies. These demonstrate that significant improvements can be made over traditional design approaches resulting in much more reusable, (re)configurable and extensible systems

    Aspect-Oriented Programming

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    Aspect-oriented programming is a promising idea that can improve the quality of software by reduce the problem of code tangling and improving the separation of concerns. At ECOOP'97, the first AOP workshop brought together a number of researchers interested in aspect-orientation. At ECOOP'98, during the second AOP workshop the participants reported on progress in some research topics and raised more issues that were further discussed. \ud \ud This year, the ideas and concepts of AOP have been spread and adopted more widely, and, accordingly, the workshop received many submissions covering areas from design and application of aspects to design and implementation of aspect languages

    Liberating Composition from Language Dictatorship

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    Historically, programming languages have been—although benevolent—dictators: fixing a lot of semantics into built-in language constructs. Over the years, (some) programming languages have freed the programmers from restrictions to use only built-in libraries, built-in data types, or built-in type checking rules. Even though, arguably, such freedom could lead to anarchy, or people shooting themselves in the foot, the contrary tends to be the case: a language that does not allow for extensibility, is depriving software engineers from the ability to construct proper abstractions and to structure software in the most optimal way. Instead, the software becomes less structured and maintainable than would be possible if the software engineer could express the behavior of the program with the most appropriate abstractions. The new idea proposed by this paper is to move composition from built-in language constructs to programmable, first-class abstractions in the language. As an emerging result, we present the Co-op concept of a language, which shows that it is possible with a relatively simple model to express a wide range of compositions as first-class concepts

    Architectural reflection for software evolution

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    Software evolution is expensive. Lehman identifies several problems associated with it: Continuous adaptation, increasing complexity, continuing growth, and declining quality. This paper proposes that a reflective software engineering environment will address these problems by employing languages and techniques from the software architecture community. Creating a software system will involve manipulating a collection of views, including low-level code views and high-level architectural views which will be tied together using reflection. This coupling will allow the development environment to automatically identify inconsistencies between the views, and support software engineers in managing architectures during evolution. This paper proposes a research programme which will result in a software engineering environment which addresses problems of software evolution and the maintenance of consistency between architectural views of a software system
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