David D. Langan

A cognitive-based approach to introductory computer science courses: lesson learned

A project has been undertaken this past year using a cognitive based approach to implement the Computing I and II courses as defined in Implementation D of Computing Curricula 1991. The salient features of this project include: (i) strategic sequencing and associated levels of mastery of key topics based on Bloom levels; (ii) a spiral approach to presentation; (iii) integral use of structured closed labs; (iv) frequent feedback and (v) early use of teams. This project has led to a series of course documents that explicitly define and schedule course micro-objectives, that map each micro-objective to a specific Bloom knowledge level, and that help to achieve and measure those objectives.

A voice-activated syntax-directed editor for manually disabled programmers

This paper discusses a research project targeted at the design and implementation of an interface intended to allow manually disabled people to more easily perform the task of programming. It proposes a Speech User Interface (SUI) targeted for this task. Voice was selected as the means of input as an alternative to the keyboard and mouse. Traditional programming IDEs tend to be character and line oriented. It is argued that this orientation is not conducive to voice input, and so a syntaxdirected programming interface is proposed. To test the viability of this combination of voice with a syntax-directed approach, an editor named VASDE (Voice-Activated Syntax-Directed Editor) was implemented using ECLIPSE as the underlying platform for development. This paper describes the syntax-directed interface, VASDE, and some of the lessons learned from initial usability studies.

Fast, precise flattening of cubic Bézier path and offset curves

We present two related algorithms for flattening (generating polyline approximations for) curves associated with planar cubic Bezier segments. One flattens the path curve, and the other flattens the left and right offset curves. The algorithm for flattening path curves yields an average of 67% of the vertices generated by recursive subdivision, while maintaining flatness to within 4% of the specified value, and runs 37% faster. The algorithm for flattening offset curves generates 70% of the vertices as the methods based on recursive subdivision, such that 94% of all subsegments fall within 20% of the flatness criterion. This latter code runs as fast as recursive subdivision.

A methodology for fast PC hard disk state restoration

It is often desirable to maintain a particular set of files and directories on one or more PC hard disks, The original state, where that set of files and directories is present, is called the pristine state. Files are subsequently added, deleted and modified. A common solution to the Foblem of retpming the hard disk to the pristine state is to (a) reformat the hard drive and (b) use a restore program to restore files and directories based on a set of backup-disks. This paper presenta a new methodology for performing the pristine state restoration more efficiently. The methodology, like the common approach, starts with some setup activities to capture the pristine stste (e.g., performing a standard full backup). Then three steps are used each time the restoration is performed, These steps are: ( I ) automatically restore a collection of often-modfied-files to the hard disk, (2) based on differences between the pristine state and the current state of the hard disk drive, delete fdes and directories that have been modified or added and (3) if the fust two steps have not returned the hard disk to a state equivalent to the pristine state, perform a restoration of the missing tiles or directories. If steps one and two, which require only a single disk to be loaded are suecessftrl, then most of the time consuming part of a full restoration is avoided. Test results presented sbw that this three step methodology restores a hard disk to a state equiv dent to the pristine state in 25-30% of the time required for the conventional solution.

A pattern-based development tool for mobile agents

Mobile agents are a technology that is applicable in several courses. However, the development of applications using mobile agents can be difficult and time-consuming for students. To address this problem, a tool called Mobile Agent Development Environment (MADE) is presented. MADE facilitates the rapid creation of mobile agent based applications through a pattern-based code generating wizard. MADE organizes and offers the creation of mobile agents based on their characteristics and behavior. MADE is based on the IBM Aglets API. MADE also offers easy-to-use plug-ins for course specific domains such as database and networking. Initial testing has shown that 55% of the code needed for simple applications can be generated quickly and automatically using the described tool.

Fast, precise flattening of cubic Bezier segment offset curves

A fast algorithm for generating a polyline approximation (flattening) for the offset curves of a cubic Bezier curve segment is described. It is shown to be more efficient than the standard recursive subdivision method by generating only 70% as many segments, but, just as importantly, 94% of all segments fall within 20% of the flatness criterion. The code runs as fast as recursive subdivision.

Affective objectives in a programming languages course

This paper discusses the use of affective objectives in upper-level computer science courses. The use of affective objectives can enrich student experiences, support student motivation, and enhance the achievement of the cognitive objectives. The paper documents an effort to incorporate affective objectives into a junior level programming languages course. Two affective objectives for that course are identified and two exercises used to achieve those objectives are presented. Observations from the use of these exercises led the authors to conclude that they were beneficial.

An object-oriented design for a dataflow simulator

Dataflow is a data-driven, parallel, functional execution model. Dataflow machines are being investigated as an alternative approach for high-performance machines. Unfortunately such machines are not widely available for testing purposes. This paper presents an object-oriented design for a dataflow simulator. Such a simulator provides a tool to investigate dataflow models and algorithms.

A voice-activated integrated development environment for manually disabled programmers

Purpose. The paper presents the design and implementation of voice-based interface to support two types of application development activities (coding, and visual GUI design) by manually disabled programmers. Method. Prototype programs were implemented, and tests were performed for both proposed voice-based interface models. Results. The interface design concepts, and the results and lessons learned of the usability studies are discussed. Conclusions. The usability studies indicated that the interface models were sound, although the voice recognition aspects left something to be desired.

A Model for Voice-activated Expression Editing

Code entry and editing by manually disabled computer programmers is difficult in conventional GUI-based development environments, since these rely heavily on mouse and keyboard use. The advent of accurate and responsive speech recognition technologies has made the speech user interface (SUI) a viable option for input. While high level programming constructs can be entered in a fairly natural way us / ing voice, expressions may be very complex in structure, and may use a wide variety of variables, literals, punctuation marks and operator symbols. A SUI-based syntax-directed editor was previously presented, but its interface model did not include expression editing in its model and implementation. This paper fills this gap by presenting a SUI-based model for entering and editing programming language expressions. A Java implementation was evaluated by a group of programmers to verify the functionality and to test the ease of use of the model. The results of this evaluation are presented and discussed.