incorporates features not found in earlier proposals; it is easier to use and has greater expressive power. Some of the salient features of our language are: ffl Precise model-theoretic semantics. ffl A very expressive form of path expressions that not only can do joins, selections and unnesting, but can also

This paper attempts to define an object-oriented database system. It describes the main features and characteristics that a system must have to qualify as an objectoriented database system. We have separated these characteristics into three groups: ffl Mandatory, the ones the system must satisfy

A promising technique for protecting privacy and integrity of sensitive data is to statically check information flow within programs that manipulate the data. While previous work has proposed programming language extensions to allow this static checking, the resulting languages are too restrictive for practical use and have not been implemented. In this paper, we describe the new language JFlow, an extension to the Java language that adds statically-checked information flow annotations. JFlow provides several new features that make information flow checking more flexible and convenient than in previous models: a decentralized label model, label polymorphism, run-time label checking, and automatic label inference. JFlow also supports many language features that have never been integrated successfully with static information flow control, including objects, subclassing, dynamic type tests, access control, and exceptions. This paper defines the JFlow language and presents formal rules tha...

It is increasingly important to structure signal processing algorithms and systems to allow for trading off between the accuracy of results and the utilization of resources in their implementation. In any particular context, there are typically a variety of heuristic approaches to managing these tradeoffs. One of the objectives of this paper is to suggest that there is the potential for developing a more formal approach, including utilizing current research in Computer Science on Approximate Processing and one of its central concepts, Incremental Refinement. Toward this end, we first summarize a number of ideas and approaches to approximate processing as currently being formulated in the computer science community. We then present four examples of signal processing algorithms/systems that are structured with these goals in mind. These examples may be viewed as partial inroads toward the ultimate objective of developing, within the context of signal processing design and implementation,...

From a software-technology point of view, the-kernel concept is superior to large integrated kernels. On the other hand, it is widely believed that (a)-kernel based systems are inherently inefficient and (b) they are not sufficiently flexible. Contradictory to this belief, we show and support by documentary evidence that inefficiency and inflexibility of current-kernels is not inherited from the basic idea but mostly from overloading the kernel and/or from improper implementation. Based on functional reasons, we describe some concepts which must be implemented by a-kernel and illustrate their flexibility. Then, we analyze the performance critical points. We show what performance is achievable, that the efficiency is sufficient with respect to macro-kernels and why some published contradictory measurements are not evident. Furthermore, we describe some implementation techniques and illustrate why-kernels are inherently not portable, although they improve portability of the whole system.

This document is available from http://ilk.kub.nl/~ilk/papers/ilk9901.ps.gz. All rights reserved Induction of Linguistic Knowledge, Tilburg University. Contents 1 License terms 1 2 Installation 3 3 Changes 4 4 Learning algorithms 6

This paper presents a new system, called NetSolve, that allows users to access computational resources, such as hardware and software, distributed across the network. This project has been motivated by the need for an easy-to-use, efficient mechanism for using computational resources remotely. Ease of use is obtained as a result of different interfaces, some of which do not require any programming effort from the user. Good performance is ensured by a load-balancing policy that enables NetSolve to use the computational resource available as efficiently as possible. NetSolve is designed to run on any heterogeneous network and is implemented as a fault-tolerant client-server application. Keywords Distributed System, Heterogeneity, Load Balancing, Client-Server, Fault Tolerance, Linear Algebra, Virtual Library. University of Tennessee - Technical report No cs-95-313 Department of Computer Science, University of Tennessee, TN 37996 y Mathematical Science Section, Oak Ridge National La...

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Concurrency has been expressed variously in terms of formal languages (typically via the shuffle operator), partial orders, and temporal logic, inter alia. In this paper we extract from these three approaches a single hybrid approach having a rich language that mixes algebra and logic and having a natural class of models of concurrent processes. The heart of the approach is a notion of partial string derived from the view of a string as a linearly ordered multiset by relaxing the linearity constraint, thereby permitting partially ordered multisets or pomsets. Just as sets of strings form languages, so do sets of pomsets form processes. We introduce a number of operations useful for specifying concurrent processes and demonstrate their utility on some basic examples. Although none of the operations is particularly oriented to nets it is nevertheless possible to use them to express processes constructed as a net of subprocesses, and more generally as a system consisting of components. Th...

This paper presents a generic meta-model of multi-agent systems based on organizational concepts such as groups, roles and structures. This model, called AALAADIN, defines a very simple description of coordination and negotiation schemes through multi-agent systems. Aalaadin is a meta-model of artificial organization by which one can build multi-agent systems with different forms of organizations such as market-like and hierarchical organizations. We show that this meta-model allows for agent heterogeneity in languages, applications and architectures. We also introduce the concept of organizational reflection which uses the same conceptual model to describe systemlevel tasks such as remote communication and migration of agents. Finally, we briefly describe a platform, called MADKIT, based on this model. It relies on a minimal agent kernel with platform-level services implemented as agents, groups and roles. 1 Introduction Whereas organization has been presented as a major issue of m...