Development of a prototype multi-processing interactive software invocation system

The Interactive Software Invocation System (NASA-ISIS) was first transported to the M68000 microcomputer, and then rewritten in the programming language Path Pascal. Path Pascal is a significantly enhanced derivative of Pascal, allowing concurrent algorithms to be expressed using the simple and elegant concept of Path Expressions. The primary results of this contract was to verify the viability of Path Pascal as a system's development language. The NASA-ISIS implementation using Path Pascal is a prototype of a large, interactive system in Path Pascal. As such, it is an excellent demonstration of the feasibility of using Path Pascal to write even more extensive systems. It is hoped that future efforts will build upon this research and, ultimately, that a full Path Pascal/ISIS Operating System (PPIOS) might be developed

Confluent Orthogonal Drawings of Syntax Diagrams

We provide a pipeline for generating syntax diagrams (also called railroad diagrams) from context free grammars. Syntax diagrams are a graphical representation of a context free language, which we formalize abstractly as a set of mutually recursive nondeterministic finite automata and draw by combining elements from the confluent drawing, layered drawing, and smooth orthogonal drawing styles. Within our pipeline we introduce several heuristics that modify the grammar but preserve the language, improving the aesthetics of the final drawing.Comment: GD 201

A project to investigate mechanisms and methodologies for the design and construction of communicating concurrent processes in real-time environments

Research undertaken in 1979 into effective and appropriate mechanisms to aid in the design and construction of software for use in the flight research programs undertaken by NASA is presented

Exact conjectured expressions for correlations in the dense O(1)(1) loop model on cylinders

We present conjectured exact expressions for two types of correlations in the dense O$(n=1)$ loop model on $L\times \infty$ square lattices with periodic boundary conditions. These are the probability that a point is surrounded by $m$ loops and the probability that $k$ consecutive points on a row are on the same or on different loops. The dense O$(n=1)$ loop model is equivalent to the bond percolation model at the critical point. The former probability can be interpreted in terms of the bond percolation problem as giving the probability that a vertex is on a cluster that is surrounded by \floor{m/2} clusters and \floor{(m+1)/2} dual clusters. The conjectured expression for this probability involves a binomial determinant that is known to give weighted enumerations of cyclically symmetric plane partitions and also of certain types of families of nonintersecting lattice paths. By applying Coulomb gas methods to the dense O$(n=1)$ loop model, we obtain new conjectures for the asymptotics of this binomial determinant.Comment: 17 pages, replaced by version accepted by JSTA

An operating system for future aerospace vehicle computer systems

The requirements for future aerospace vehicle computer operating systems are examined in this paper. The computer architecture is assumed to be distributed with a local area network connecting the nodes. Each node is assumed to provide a specific functionality. The network provides for communication so that the overall tasks of the vehicle are accomplished. The O/S structure is based upon the concept of objects. The mechanisms for integrating node unique objects with node common objects in order to implement both the autonomy and the cooperation between nodes is developed. The requirements for time critical performance and reliability and recovery are discussed. Time critical performance impacts all parts of the distributed operating system; e.g., its structure, the functional design of its objects, the language structure, etc. Throughout the paper the tradeoffs - concurrency, language structure, object recovery, binding, file structure, communication protocol, programmer freedom, etc. - are considered to arrive at a feasible, maximum performance design. Reliability of the network system is considered. A parallel multipath bus structure is proposed for the control of delivery time for time critical messages. The architecture also supports immediate recovery for the time critical message system after a communication failure

Toward an automaton Constraint for Local Search

We explore the idea of using finite automata to implement new constraints for local search (this is already a successful technique in constraint-based global search). We show how it is possible to maintain incrementally the violations of a constraint and its decision variables from an automaton that describes a ground checker for that constraint. We establish the practicality of our approach idea on real-life personnel rostering problems, and show that it is competitive with the approach of [Pralong, 2007]

A Tutorial Introduction to Mosaic Pascal

In this report we describe a Pascal system that has been developed for programming Mosaic multi- computers. The system that we discuss runs on our Sun workstations, and we assume some familiarity with the use thereof. We assume the reader to be also familiar with programming in Pascal, and with message-passing programs. We describe how the Pascal language has been extended to perform message passing. We discuss a few implementation aspects that are relevant only to those users who have a need (or desire) to control some machine-specific aspects. The latter requires some detailed knowledge of the Mosaic system

The CAITLIN Auralization System: Hierarchical Leitmotif Design as a Clue to Program Comprehension

Early experiments have suggested that program auralization can convey information about program structure [8]. Languages like Pascal contain classes of construct that are similar in nature allowing hierarchical classification of their features. This taxonomy can be reflected in the design of musical signatures which are used within the CAITLIN program auralization system. Experiments using these hierarchical leitmotifs indicate whether or not their similarities can be put to good use in communicating information about program structure and state

EOS: A project to investigate the design and construction of real-time distributed embedded operating systems

The EOS project is investigating the design and construction of a family of real-time distributed embedded operating systems for reliable, distributed aerospace applications. Using the real-time programming techniques developed in co-operation with NASA in earlier research, the project staff is building a kernel for a multiple processor networked system. The first six months of the grant included a study of scheduling in an object-oriented system, the design philosophy of the kernel, and the architectural overview of the operating system. In this report, the operating system and kernel concepts are described. An environment for the experiments has been built and several of the key concepts of the system have been prototyped. The kernel and operating system is intended to support future experimental studies in multiprocessing, load-balancing, routing, software fault-tolerance, distributed data base design, and real-time processing