ABSTRACT: In previous heap storage systems, the cost of creating objects and garbage collection is independent of the lifetime of the object. Since objects with short lifetimes account for a large portion of storage use, it is worth optimizing a garbage collector to reclaim storage for these objects more quickly. The garbage collector should spend proportionately less effort reclaiming objects with longer lifetimes. We present a garbage collection algorithm that (1) makes storage for short-lived objects cheaper than storage for long-lived objects, (2) that operates in real-time--object creation and access times are bounded, (3) increases locality of reference, for better virtual memory performance, (4) works well with multiple processors and a large address space. 1.

We present an interpretation of typed object-oriented concepts in terms of well-understood, purely procedural concepts. More precisely, we give a compositional subtypepreserving translation of a basic object calculus supporting method invocation, functional method update, and subtyping, into the polymorphic -calculus with recursive types and subtyping. The translation techniques apply also to an imperative version of the object calculus which includes inplace method update and object cloning. Finally, the translation easily extends to "Self types" and other interesting object-oriented constructs. 1 Introduction Object-oriented programming languages have introduced numerous ideas, structures, and techniques. Although these contributions are not always conceptually clear (or even sound), they are often original and useful. One of the most basic contributions is the notion of self; the operations associated with an object (its methods) can refer to the object as self, and invoke other op...

This paper discusses knowledge sharing (inheritance) mechanisms for Object-Oriented Programming (OOP) in the context of concurrent (distributed) languages. We review three different schemes: inheritance, delegation and copy. A fourth model, called recipe-query, is presented and all are compared and criticized. Techniques relying on the shared memory assumption are rejected. We point out the conflict between distributing knowledge among objects and the synchronization of concurrent objects. Keywords: objects, classes, actors, message passing, knowledge sharing, inheritance, subclassing, delegation, proxies, code sharing, copy, synchronization, atomicity, distributed systems. 1 Introduction 1.1 Knowledge Sharing for Modularity and Classification Knowledge sharing (or inheritance) is a mechanism intensively used in OOP. Its basic idea is the reuse of object descriptions. After defining an object, we would often like to refine it into a more specialized one. Rather than defining a new ...

In this paper we will address several architectural decisions in defining a software control architecture for mobile robots. Our system is a collection of control primitives that enables the development of simulations or control algorithms for autonomous agents. Its computational capabilities are determined by an object-oriented constraint-based architecture. We discuss how high level knowledge, skills, goal-driven and reactive behavior are integrated within such an architecture. Our goal is to design a framework that enables the merging of classic and reactive implementation ideas. We will show, that each such type of control can be implemented in our system. The issues of task decomposition and granularity are given special attention, as they lie at the basis of our architecture. We discuss two learning methods supported by our system. The first is based on environment exploration, while the second copes with skill acquisition. Our robot, cyclops , is a LEGO mini-robot based on the 6...

This paper opens by discussing what is meant by the term interoperability, the motivations for building such systems and the characteristics and issues surrounding self describing reflective information systems. A brief summary of current standardisation work follows together with an analysis of how this might impact on the future design of HEP production management systems. The paper concludes with a section on the experiences gained in applying these ideas to a production management system for an experiment detector.

In previous heap storage systems, the cost of creating objects and garbage collection is independent of the lifetime of the object. Since objects with short lifetimes account for a large portion of storage use, it is worth optimizing a garbage collector to reclaim storage for these objects more quickly. The garbage collector should spend proportionately less effort reclaiming objects with longer lifetimes. We present a garbage collection algorithm that (1) makes storage for short-lived objects cheaper than storage for long-lived objects, (2) that operates in real-time--object creation and access times are bounded, (3) increases locality of reference, for better virtual memory performance, (4) works well with multiple processors and a large address space. 1.