44497725
Simulation of information flow in organizations
The Icarus simulation system is the result of an experiment in embedding small rule-based expert systems into a discrete event simulation environment. The goal of this work is to allow the use of expert systems to model the intelligent behavior of people that are included in the system being simulated. The major problems we have encountered in building the Icarus system have resulted from unexpected and fundamental interactions between expert systems and our discrete event simulation framework. These interactions are the focus of this paper.
14144660
Systematic protection mechanism design
This work describes an attempt to systematically design a hardware resource protection mechanism when given the requirements of a particular language as a target. The design process is formalized as a structured walk through the multidimensional computer design space towards a hypothetical class of optimal machines. Each step in this walk involves a change in the distribution of work between the compiler and run-time system but no change in the source language semantics. The starting point for this walk is the result of a semantic analysis of the language to be implemented; typically, this produces a very high level machine where the compiler, if any, is trivial. The walk ends when no changes result in a net improvement. This does not guarantee that the result is even locally optimal, since the changes tried depend on the ingenuity and persistence of the designer.
 This design approach has been used to arrive at a practical, general purpose protection mechanism oriented towards the needs of the Ada language (preliminary version). This architecture was evaluated by comparing it with the PDP-11/45. For the purpose of this comparison, the protection mechanism was incorporated into a partially specified PDP-11 like instruction set. The number of bits making up the processor state and the number of operations involved in address computation were evaluated. On this basis, the result appears to be competitive and worth further investigation.
12941967
Application of splay trees to data compression
The splay-prefix algorithm is one of the simplest and fastest adaptive data compression algorithms based on the use of a prefix code. The data structures used in the splay-prefix algorithm can also be applied to arithmetic data compression. Applications of these algorithms to encryption and image processing are suggested.
17285109
Concurrent operations on priority queues
Among the fastest priority queue implementations, skew heaps have properties that make them particularly suited to concurrent manipulation of shared queues. A concurrent version of the top down implementation of skew heaps can be produced from previously published sequential versions using almost mechanical transformations. This implementation requires O(log n) time to enqueue or dequeue an item, but it allows new operations to begin after only O(1) time on a MIMD machine. Thus, there is potential for significant concurrency when multiple processes share a queue. Applications to problems in graph theory and simulation are discussed in this article.
14456192
Improved interpretation of UNIX-like file names embedded in data
When the data processed by a program span several files, the common practice of including file names as data in some of the files leads to difficulties in moving or sharing that data. In systems using tree structured directories, this problem can be solved by making a syntactic distinction between absolute and relative file names.
42995338
Assembly Language as Object Code
The set of meanings that may be encoded in most object languages is a subset of the meanings that may be encoded in most assembly languages. Careful exploitation of this fact in the design of the SMAL assembly and object language allows the SMAL assembler itself to be used as a linkage editor, thus eliminating the need for an expensive and often misunderstood system program. The SMAL assembler is no more complex than many assemblers in common use today, nor are the relevant aspects of the SMAL language particularly unique.
7107822
Minimax disappointment criterion for video broadcasting
Users of media broadcasting services generally experience different grades of overall performance because of the non-uniform quality of their channel conditions. In order to provide all users equally satisfactory performance, we propose a new performance criterion named "minimax disappointment", based on layered service levels and the basic principle of joint source-channel coding. This criterion minimizes for all users the maximum value of performance degradation between the received performance and the expected optimal performance, given each user's individual channel situation. In support of this criterion, we develop two broadcasting systems and a gradient-based optimization scheme. Our systems achieve universally near-maximal performance for multiple user classes by providing layered service.
6816511
Joint source channel matching for a wireless communications link
Summary form only given. With the rapid growth of wireless communications systems there is an increasing demand for efficient image and video transmission. Significant performance gains can be obtained from joint source channel matching where system resources are assigned based on the tradeoff between data and redundancy. We develop a more general approach for joint source channel matching based on a parametric distortion model that incorporates the flexibility and constraints of both the source and the channel. We use parametric models describing source and channel. We use parametric models describing source and channel characteristics that can be accurately applied to most classes of source and channel coders. To show the generality of our approach, we applied it to the familiar Said-Pearlman progressive image coder with two types of channel coders, a coder with orthogonal symbols of different power, and fixed-rate BPSK modulation overlaid with Reed Solomon codes.
37553153
MultiGen: an integrated multiple-objective solution system
This paper presents an overview of a global multiple-objective system capable of rigourously handling a wide variety of multiple-objective and goal programming (GP) models. The system has two efficient solution engines that complement one another. These are an intelligent conventional optimisation system and a genetically driven heuristic search-based solver. The development of a linear and nonlinear sparse storage system capable of handling additional multiple-objective factors such as priority levels, goals, objectives, and upper and lower bounds is described. An appropriate input/output style for multiple-objective programmes is given. The resulting package provides an efficient and user-friendly environment for the interactive solution and analysis of a wide variety of multiple-objective programming (MOP) models.
16917081
Role of Word Sense Disambiguation in Lexical Acquisition: Predicting Semantics from Syntactic Cues
This paper addresses the issue of word-sense ambiguity in extraction from machine-readable resources for the construction of large-scale knowledge sources. We describe two experiments: one which ignored word-sense distinctions, resulting in 6.3% accuracy for semantic classification of verbs based on (Levin, 1993); and one which exploited word-sense distinctions, resulting in 97.9% accuracy. These experiments were dual purpose: (1) to validate the central thesis of the work of (Levin, 1993), i.e., that verb semantics and syntactic behavior are predictably related; (2) to demonstrate that a 15-fold improvement can be achieved in deriving semantic information from syntactic cues if we first divide the syntactic cues into distinct groupings that correlate with different word senses. Finally, we show that we can provide effective acquisition techniques for novel word senses using a combination of online sources.
29355557
Hyper-spherical inversion transformations in multi-objective evolutionary optimization
Abstract Multi-objective evolutionary algorithms (MOEAs) are widely considered to have two goals: convergence towards the true Pareto front and maintaining a diverse set of solutions. The primary concern here is with the first goal of convergence, in particular when one or more variables must converge to a constant value. Using a number of well known test problems, the difficulties that are currently impeding convergence are discussed and then a new method is proposed that transforms the decision space using the geometric properties of hyper-spherical inversions to converge towards/onto the true Pareto front. Future extensions of this work and its application to multi-objective optimisation is discussed.