42 research outputs found

    Towards Adaptable and Adaptive Policy-Free Middleware

    Get PDF
    We believe that to fully support adaptive distributed applications, middleware must itself be adaptable, adaptive and policy-free. In this paper we present a new language-independent adaptable and adaptive policy framework suitable for integration in a wide variety of middleware systems. This framework facilitates the construction of adaptive distributed applications. The framework addresses adaptability through its ability to represent a wide range of specific middleware policies. Adaptiveness is supported by a rich contextual model, through which an application programmer may control precisely how policies should be selected for any particular interaction with the middleware. A contextual pattern mechanism facilitates the succinct expression of both coarse- and fine-grain policy contexts. Policies may be specified and altered dynamically, and may themselves take account of dynamic conditions. The framework contains no hard-wired policies; instead, all policies can be configured.Comment: Submitted to Dependable and Adaptive Distributed Systems Track, ACM SAC 200

    TOQL: Temporal Ontology Querying Language

    Full text link

    CallE: An Effect System for Method Calls

    Full text link
    Effect systems are used to statically reason about the effects an expression may have when evaluated. In the literature, such effects include various behaviours as diverse as memory accesses and exception throwing. Here we present CallE, an object-oriented language that takes a flexible approach where effects are just method calls: this works well because ordinary methods often model things like I/O operations, access to global state, or primitive language operations such as thread creation. CallE supports both flexible and fine-grained control over such behaviour, in a way designed to minimise the complexity of annotations. CallE's effect system can be used to prevent OO code from performing privileged operations, such as querying a database, modifying GUI widgets, exiting the program, or performing network communication. It can also be used to ensure determinism, by preventing methods from (indirectly) calling non-deterministic primitives like random number generation or file reading

    A Statically Typed Logic Context Query Language With Parametric Polymorphism and Subtyping

    Get PDF
    The objective of this thesis is programming language support for context-sensitive program adaptations. Driven by the requirements for context-aware adaptation languages, a statically typed Object-oriented logic Context Query Language  (OCQL) was developed, which is suitable for integration with adaptation languages based on the Java type system. The ambient information considered in context-aware applications often originates from several, potentially distributed sources. OCQL employs the Semantic Web-language RDF Schema to structure and combine distributed context information. OCQL offers parametric polymorphism, subtyping, and a fixed set of meta-predicates. Its type system is based on mode analysis and a subset of Java Generics. For this reason a mode-inference approach for normal logic programs that considers variable aliasing and sharing was extended to cover all-solution predicates. OCQL is complemented by a service-oriented context-management infrastructure that supports the integration of OCQL with runtime adaptation approaches. The applicability of the language and its infrastructure were demonstrated with the context-aware aspect language CSLogicAJ. CSLogicAJ aspects encapsulate context-aware behavior and define in which contextual situation and program execution state the behavior is woven into the running program. The thesis concludes with a case study analyzing how runtime adaptation of mobile applications can be supported by pure object-, service- and context-aware aspect-orientation. Our study has shown that CSLogicAJ can improve the modularization of context-aware applications and reduce anticipation of runtime adaptations when compared to other approaches

    The Reflex Sandbox : an experimentation environment for an aspect-oriented Kernel

    Get PDF
    Reflex es un núcleo versátil para la programación orientada aspectos en Java. Provee de las abstracciones básicas, estructurales y de comportamiento, que permiten implementar una variedad de técnicas orientadas a aspectos. Esta tesis estudia dos tópicos fundamentales. En primer lugar, el desarrollo formal, utilizando el lenguaje Haskell, de las construcciones fundamentales del modelo Reflex para reflexión parcial de comportamiento. Este desarrollo abarca el diseño de un lenguaje, llamado Kernel, el cual es una extensión reflexiva de un lenguaje orientado a objetos simple. La semántica operacional del lenguaje Kernel es presentada mediante una máquina de ejecución abstracta. El otro tópico fundamental que estudia esta tesis es validar que el modelo de reflexión parcial de comportamiento es suficientemente expresivo para proveer de semántica a un subconjunto del lenguaje AspectJ. Con este fin, se desarrolló el Reflex Sandbox: un ambiente de experimentación en Haskell para el modelo Reflex. Tanto el desarrollo formal del modelo de reflexión parcial de comportamiento como la validación del soporte de AspectJ, son estudiados en el contexto del Reflex Sandbox. La validación abarca la definición de un lenguaje orientado a aspectos que caracteriza el enfoque de AspectJ a la programación orientada a aspectos, así como la definición de su máquina de ejecución abstracta. También se presenta un compilador que transforma programas escritos en este lenguaje al lenguaje Kernel. Este proceso de compilación provee los fundamentos para entender como dicha transformación puede ser realizada. El proceso de compilación también fue implementado en Java, pero transformando programas AspectJ a programas Reflex. También se presentan mediciones preliminares del desempeño de un programa compilado y ejecutado en Reflex y un programa compilado, y ejecutado con el compilador AspectJ
    corecore