Software Engineering and Programming Languages
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Computer system reliability and nuclear war
Given the devastating consequences of nuclear war, it is appropriate to look at current and planned uses of computers in nuclear weapons command and control systems, and to examine whether these systems can fulfill their intended roles.
An improved parallel thinning algorithm
An iterative thinning algorithm reduces a two-dimensional pattern of strokes to its skeleton by removing layers of edge elements until each stroke has unit thickness. A parallel solution requires the independent calculation of new values for each iteration, using a window of nearest neighbors for each element. The traditional need for at least two subiterations can be avoided by modifying the window to permit the availability of intermediate calculations. Timings on an ICL DAP (an array processor) indicate an improvement of over 40 percent. Additional refinements are suggested to reduce noise in the final skeleton.
Systolic algorithms to examine all pairs of elements
Four methods to solve the all pairs examination problem are presented. The first two methods are based on the fold-over scheme. The remaining two methods are adopted from some parallel sorting algorithms. All of these approaches can be implemented on a linear systolic array.
COBOL on a PC: a new perspective on a language and its performance
A comparison of Cobol performance on the PC AT Enhanced versus an IBM 370 mainframe suggests that high-quality PC compiler implementations—combined with the new language features of the Cobol 85 Standard—are improving the PC environment for Cobol to the point where serious applications can now be developed and debugged on the PC, either to be run on the PC itself, or for eventual uploading to a mainframe.
MATCH—a new high-level relational operator for pattern matching
Pattern matching is a common and fundamental operation of many applications, such as expert systems (ES). With continued growth the knowledge bases of such systems will need database management systems (DBMS) support. Providing this support will require extending DBMS to meet the needs of these systems. We have developed an operator that extends the relational data model to do pattern matching with very complex stored patterns.
Beyond the chalkboard: computer support for collaboration and problem solving in meetings
Although individual use of computers is fairly widespread, in meetings we tend to leave them behind. At Xerox PARC, an experimental meeting room called the Colab has been created to study computer support of collaborative problem solving in face-to-face meetings. The long-term goal is to understand how to build computer tools to make meetings more effective.
A relational information resource dictionary system
A relational implementation of IRDS using SQL demonstrates how the flexibility of the relational environment enhances the extensibility of the IRDS while at the same time providing more powerful dictionary capabilities than are typically found in relational systems.
Interface design issues for advice-giving expert systems
Advice giving could become the first successful domain for intelligent interfaces.
Contention is no obstacle to shared-memory multiprocessing
Contention in large-scale shared-memory systems is less of a concern than generally believed. Through careful engineering of a parallel system, the effects of contention can be controlled.
The intensive use of memory to recall specific episodes from the past—rather than rules—should be the foundation of machine reasoning.
Parallel free-text search on the connection machine system
A new implementation of free-text search using a new parallel computer—the Connection Machine®—makes possible the application of exhaustive methods not previously feasible for large databases.
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