Systems and Networking
Advertisement
The impact of robotics on computer science
The rapid development of robotics and the resulting need for computer scientists to be better trained in traditional mathematics necessitate changes in computer science curricula.
Normalization of relations and PROLOG
A program for the normalization of relations that is written in Prolog has several advantages relative to programs written in conventional programming languages: notably, conciseness and clarity. The program presented here implements several normalization algorithms and is suitable for the interactive design of small database applications and as a teaching aid.
Opportunities for research on numerical control machining
Numerical control (NC) machining could be reinvigorated by adapting robotic software technology. Regrettably, pressures are mounting in industry to constrain robots to NC standards, and the academic community views NC as an obsolete, solved problem, with little remaining scholarly challenge. Grossman examines the current status of APT, an NC language, and proposes the merging of APT with a modern robotics language.
A music-description language designed to facilitate both electronic communication and publication-quality printing of musical scores incorporates a syntax for expressing concurrency and two-dimensionality and places new demands on text formatters.
Abstraction-based software development
A five-year experience with abstraction-based software-development techniques in the university environment indicates that the investment required to support the paradigm in practice is returned in terms of greater ability to control complexity in large projects—provided there exists a set of software tools sufficient to support the approach.
TID—a translation invariant data structure for storing images
There are a number of techniques for representing pictorial information, among them are borders, arrays, and skeletons. Quadtrees are often used to store black and white picture information. A variety of techniques have been suggested for improving quadtrees, including linear quadtrees, QMATs (quadtree medial axis transform), forests of quadtrees, etc. The major purpose of these improvements is to reduce the storage required without greatly increasing the processing costs. All of these methods suffer from the fact that the structure of the underlying quadtree can be very sensitive to the placement of the origin.
In this paper we discuss a translation invariant data structure (which we name TID) for storing and processing images based on the medial axis transform of the image that consists of all the maximal black squares contained in the image. We also discuss the performance of TID with other existing structures such as QMATs, forests of quadtrees, and normalized quadtrees. Some discussion on the union and intersection of images using TID is included.
Novel security techniques for online systems
By ensuring entry to subsystems (zones) with different facilities and security levels, log-in procedures can do more than simply delay illicit access.
The British Nationality Act as a logic program
The formalization of legislation and the development of computer systems to assist with legal problem solving provide a rich domain for developing and testing artificial-intelligence technology.
An empirical comparison of priority-queue and event-set implementations
Execution times for a variety of priority-queue implementations are compared under the hold model, showing many to be faster than implicit heaps.
Positive alternatives: a report on an ACM panel on hacking
A broad cross section of computer security experts, hackers, educators, journalists, and corporate executives examine hacking issues, problems, and possible solutions.
A computer science perspective of bridge design
What kinds of lessons does a classical engineering discipline like bridge design have for an emerging engineering discipline like computer systems design? Case-study editors Alfred Spector and David Gifford consider the insight and experience of bridge designer Gerard Fox to find out how strong the parallels are.
Embedded menus: selecting items in context
In many situations, embedded menus represent an attractive alternative to the more traditional explicit menus, particularly in touchtext, spelling checkers, language-based program editors, and graphics-based systems.
Computers, complexity, and the Statue of Liberty restoration
Twentieth-century techniques such as computer-aided engineering and finite-element analysis were used to restore the nineteenth-century monument.
A locally adaptive data compression scheme
A data compression scheme that exploits locality of reference, such as occurs when words are used frequently over short intervals and then fall into long periods of disuse, is described. The scheme is based on a simple heuristic for self-organizing sequential search and on variable-length encodings of integers. We prove that it never performs much worse than Huffman coding and can perform substantially better; experiments on real files show that its performance is usually quite close to that of Huffman coding. Our scheme has many implementation advantages: it is simple, allows fast encoding and decoding, and requires only one pass over the data to be compressed (static Huffman coding takes two passes).
Shape the Future of Computing
ACM encourages its members to take a direct hand in shaping the future of the association. There are more ways than ever to get involved.
Get InvolvedCommunications of the ACM (CACM) is now a fully Open Access publication.
By opening CACM to the world, we hope to increase engagement among the broader computer science community and encourage non-members to discover the rich resources ACM has to offer.
Learn More