Reflection has attracted considerable attention in recent years. However there are very little systems that fully support reflective programming and are in real use. In this paper we try to understand the reasons for this lacking acceptance of fully reflective systems and explain how our own reflective Java system, metaXa, tries to tackle some of these problems.

An important goal of an operating system is to make computing and communication resources available in a fair and efficient way to the applications that will run on top of it. To achieve this result, the operating system implements a number of policies for allocating resources to, and sharing resources among applications, and it implements safety mechanisms to guard against misbehaving applications. However, for most of these allocation and sharing tasks, no single optimal policy exists. Different applications may prefer different operating system policies to achieve their goals in the best possible way. A customizable or adaptable operating system is an operating system that allows for flexible modification of important system policies. Over the past decade, a wide range of approaches for achieving customizability has been explored in the operating systems research community. In this survey, an overview of these approaches, structured around a taxonomy, is presented.

Classical object properties such as encapsulation ease the construction of distributed systems. The object paradigm supports modeling of real world problems in a natural way and delivers units of distribution to the resource management level. To enhance the performance of distributed systems, more detailed application-specific information like potential communication dependencies should be exploited. To fulfill

Developing distributed applications is a difficult task due to three major problems: the complexity of programming interprocess communication, the need to support services across heterogeneous platforms, and the need to adapt to changing conditions. Traditional middleware

Traditional configurable operating systems typically provide a fixed and limited set of functionality. We propose a metalevel architecture, where application-defined objects can choose from a rich selection of possible configurations and are therefore able to dynamically change the way in which they are executed to the configuration that suits best. This allows applications to adapt operating system behaviour to even unanticipated requirements during run-time. A distributed application processing multimedia data serves as an example to illustrate the concepts described. 1 Introduction Traditional configurable operating systems typically provide a fixed and limited set of functionality. With the advent of a new generation of applications such as multimedia systems, where the applications must be able to adapt to 2 TIGGER 2 changing requirements during run-time, such limited operating system support may be a hinderence to maintaining the level of efficieny these operating systems were...

Embedded systems require run-time platforms that are tailored for the specific application's needs. Extending on existing technology for flexible system software, this paper presents a generative approach for building tailormade run-time platforms from generic software components. Generic components are pre-fabricated building blocks providing generic parameters in order to tailor them for the solution of specific problems. The values of these generic parameters are chosen based on requirements that are derived from the target application. Generators then allow to instantiate generic components to customized software elements with minimal manual intervention. Important prerequisites for this approach are techniques for generic component implementations, for describing requirements on the run-time platform, and for describing component properties in a way that they can sensibly be processed by tools. The paper scetches the overall approach and highlights selected techniques addressing t...

this paper presents our point of view to the underlying concepts: reflection and runtime representations of abstractions. After that, the class-object architecture of CHEOPS is introduced. Section 4 gives a short impression about the implementation of this architecture based on C++. Finally other related and future work is discussed. 2 Reflection and runtime representations of abstractions

Traditional object-oriented real-time systems are often limited in that they provide only one approach to real-time object support. Taking the increasing demand for flexible and extensible object support environments into account, we discuss the design and implementation of a small object-oriented real-time executive based on a sub-framework which we call Roo. Roo is a component of the Tigger framework (our proposal for an extensible object support operating system) and is intended to support different object models providing soft real-time behaviour. Roo provides support for different mechanisms and policies for real-time thread management, scheduling and synchronization. In this it serves as a basis for other components of the Tigger framework. 1 Introduction Traditional object-oriented real-time systems like [16, 11] are often limited in that they provide only one approach to real-time object support. As [21] points out, for programmers using these systems this sometimes presents a...

This paper describes our experiences in porting a distributed object oriented real-time operating system called Apertos 1 to a new RISC platform, and some enhancements made to improve its performance. Apertos employs an objectmetaobject hierarchy to facilitate object heterogeneity. This meta-hierarchy is intended to support various objects with different requirements such as real-time constraints. As such a system grows, satisfying differing object requirements via the meta-hierarchy with its related communication overheads is orthogonal to achieving real-time response performance. To address this, we introduce preemptive scheduling and a hierarchical scheduling solution. I. INTRODUCTION The object-oriented paradigm and object-oriented systems have been the focus of much research in recent years. Despite their popularity, object-oriented systems have generally been implemented on top of traditional operating systems where little support is provided for objects at the kernel level. T...

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