Jean-Marie Burkhardt

Object-Oriented Program Comprehension: Effect of Expertise, Task and Phase

The goal of our study is to evaluate the effect on program comprehension of three factors that have not previously been studied in a single experiment. These factors are programmer expertise (expert versus novice), programming task (documentation versus reuse), and the development of understanding over time (phase 1 versus phase 2). This study is carried out in the context of the mental model approach to comprehension based on van Dijk and Kintschs model [(1983) Strategies of Discourse Comprehension. New York: Academic]. One key aspect of this model is the distinction between two kinds of representation the reader might construct from a text: (1) the textbase, which refers to what is said in the text and how it is said, and (2) the situation model, which represents the situation referred to by the text. We have evaluated the effect of the three factors mentioned above on the development of both the textbase (or program model) and the situation model in object-oriented program comprehension. We found a four-way interaction of expertise, phase, task and type of model. For the documentation group we found that experts and novices differ in the elaboration of their situation model but not their program model. There was no interaction of expertise with phase and type of model in the documentation group. For the reuse group, there was a three-way interaction between phase, expertise and type of model. For the novice reuse group, the effect of the phase was to increase the construction of the situation model but not the program model. With respect to the task, our results show that novices do not spontaneously construct a strong situation model but are able to do so if the task demands it.

A Methodological Framework for Socio-Cognitive Analyses of Collaborative Design of Open Source Software

Open Source Software (OSS) development challenges traditional software engineering practices. In particular, OSS projects are managed by a large number of volunteers, working freely on the tasks they choose to undertake. OSS projects also rarely rely on explicit system-level design, or on project plans or schedules. Moreover, OSS developers work in arbitrary locations and collaborate almost exclusively over the Internet, using simple tools such as email and software code tracking databases (e.g. CVS).All the characteristics above make OSS development akin to weaving a tapestry of heterogeneous components. The OSS design process relies on various types of actors: people with prescribed roles, but also elements coming from a variety of information spaces (such as email and software code). The objective of our research is to understand the specific hybrid weaving accomplished by the actors of this distributed, collective design process. This, in turn, challenges traditional methodologies used to understand distributed software engineering: OSS development is simply too “fibrous” to lend itself well to analysis under a single methodological lens.In this paper, we describe the methodological framework we articulated to analyze collaborative design in the Open Source world. Our framework focuses on the links between the heterogeneous components of a project’s hybrid network. We combine ethnography, text mining, and socio-technical network analysis and visualization to understand OSS development in its totality. This way, we are able to simultaneously consider the social, technical, and cognitive aspects of OSS development. We describe our methodology in detail, and discuss its implications for future research on distributed collective practices.

Influence of control/display ratio on the perception of mass of manipulated objects in virtual environments

This paper describes two psychophysical experiments which were conducted to evaluate the influence of the control/display (C/D) ratio on the perception of mass of manipulated objects in virtual environments (VE). In both experiments, a discrimination task was used in which participants were asked to identify the heavier object between two virtual balls. Participants could weigh each ball via a haptic interface and look at its synthetic display on a computer screen. Unknown to the participants, two parameters varied between each trial: the difference of mass between the balls and the C/D ratio used in the visual display when weighing the comparison ball. The data collected demonstrated that the C/D ratio significantly influenced the result of the mass discrimination task and sometimes even reversed it. The absence of gravity force largely increased this effect. These results suggest that if the visual motion of a manipulated virtual object is amplified when compared to the actual motion of the users hand (i.e. if the C/D ratio used is smaller than 1), the user tends to feel that the mass of the object decreases. Thus, decreasing or amplifying the motions of the user in a VE can strongly modify the perception of haptic properties of objects that he/she manipulates. Designers of virtual environments could use these results for simplification considerations and also to avoid potential perceptual aberrations.

Mental Representations Constructed by Experts and Novices in Object-Oriented Program Comprehension

Previous studies on program comprehension were carried out largely in the context of procedural languages. Our purpose is to develop and evaluate a cognitive model of object-oriented (00) program understanding. Our model is based on the van Dijk and Kintschs model of text understanding (1983). One key aspect of this theoretical approach is the distinction between two kinds of representation the reader might construct from a text: the textbase and the situation model. On the basis of results of an experiment we have conducted, we evaluate the cognitive validity of this distinction in 00 program understanding. We examine how the construction of these two representations is differentially affected by the programmers expertise and how they evolve differentially over time.

Multisensory VR interaction for protein-docking in the CoRSAIRe project

Proteins take on their function in the cell by interacting with other proteins or biomolecular complexes. To study this process, computational methods, collectively named protein docking, are used to predict the position and orientation of a protein ligand when it is bound to a protein receptor or enzyme, taking into account chemical or physical criteria. This process is intensively studied to discover new biological functions for proteins and to better understand how these macromolecules take on these functions at the molecular scale. Pharmaceutical research also employs docking techniques for a variety of purposes, most notably in the virtual screening of large databases of available chemicals to select likely molecular candidates for drug design. The basic hypothesis of our work is that Virtual Reality (VR) and multimodal interaction can increase efficiency in reaching and analysing docking solutions, in addition to fully a computational docking approach. To this end, we conducted an ergonomic analysis of the protein–protein current docking task as it is carried out today. Using these results, we designed an immersive and multimodal application where VR devices, such as the three-dimensional mouse and haptic devices, are used to interactively manipulate two proteins to explore possible docking solutions. During this exploration, visual, audio, and haptic feedbacks are combined to render and evaluate chemical or physical properties of the current docking configuration.

Camera Motions Improve the Sensation of Walking in Virtual Environments

This paper investigates the use of camera motions, in order to improve the sensation of walking in a Virtual Environment. A simple model of camera motion is first proposed. This model uses: (1) oscillating motions for the position of the camera, and (2) a compensation motion which changes the orientation of the camera and simulate oculomotor compensation to keep a constant focal point when walking. Then we describe two experiments which were conducted to study the characteristics of our model and the preference of the users in terms of sensation of walking. The first experiment compared the use of oscillating camera motions along the three directions of space. The oscillating motions were all preferred to the control condition (i.e. a linear motion, as if the user was driving a car). Furthermore, the participants preferred oscillating motions along the vertical axis, compared with the two other directions of space. The second experiment was focused on the use of a compensation motion. It showed that on average participants preferred a compensated motion during the walk, as compared with a motion with a constant orientation of the camera. These results are consistent with the way our body and eyes move naturally when walking in real life. Taken together, our results suggest that camera motions can considerably improve the sensation of walking in virtual environments. Camera motions could be further introduced in numerous applications of virtual reality in which the simulation of walking is important, such as: architectural visits, training simulations, or videogames.

Prototype evaluation and user-needs analysis in the early design of emerging technologies

This paper presents two case studies of prototype evaluation as a tool for user needs elicitation for emerging technologies. In the first user evaluation, a high-fidelity virtual reality prototype is used. In the second one, a low-fidelity mixed reality prototype is used. Our results show that prototypes may be a powerful a tool for eliciting user-needs, but their potentiality depends on their fidelity. In our studies, users elicit more needs when working with the high-fidelity prototypes. Furthermore, the information collected in this case is richer and more useful for design. We discuss these results as well as some factors that could help stakeholders elicit a greater number of needs for emerging technologies.

Thematic coherence and quotation practices in OSS design-oriented online discussions

This paper presents an analysis of online discussions in Open Source Software (OSS) design. The objective of our work is to understand and model the dynamics of OSS design that take place in mailing list exchanges. We show how quotation practices can be used to locate design relevant data in discussion archives. OSS developers use quotation as a mechanism to maintain the discursive context. To retrace thematic coherence in the online discussions of a major OSS project, Python, we follow how messages are linked through quotation practices. We compare our quotation-based analysis with a more conventional analysis: a thread-based of the reply-to links between messages. The advantages of a quotation-based analysis over a thread-based analysis are outlined. Our analysis reveals also the links between the social structure and elements in the discussion space and how it shapes influence in the design process.

Virtual technical trainer: learning how to use milling machines with multi-sensory feedback in virtual reality

This paper describes the use and characteristics of a virtual reality system called the virtual technical trainer (VTT). This system is dedicated to vocational training courses on using and programming numerically-controlled milling machines. It aims at replacing the conventional mechanical milling machines which are currently used in such vocational training courses. VTT proposes an interactive manipulation of a cutter of a virtual milling machine, with visual, audio and haptic (force) feedback. VTT uses a haptic device which was specifically designed for the purpose of our pedagogical application. When the virtual cutter mills a piece of material, a plastic deformation algorithm is used and the material is progressively carved. Trainees can feel the cutting effort thanks to a force feedback which varies as a function of different simulation parameters (rotation speed of the tool, type of material to carve, etc). Realistic audio feedback (which was recorded in real situations) and additional visual assistance may be added, in order to increase the perception and understanding of the milling task. A preliminary evaluation of VTT showed that this simulator could be used by vocational trainers successfully. It could help them to teach the basic principles of machining at the first stages of vocational training courses on numerically-controlled milling machines.

An Empirical Study of Software Reuse by Experts in Object-Oriented Design

This paper presents an empirical study of the software reuse activity by expert designers in the context of object-oriented design. Our study focuses on the three following aspects of reuse : (1) the interaction between some design processes, e.g. constructing a problem representation, searching for and evaluating solutions, and reuse processes, i.e. retrieving and using previous solutions, (2) the mental processes involved in reuse, e.g. example-based retrieval or bottom-up versus top-down expanding of the solution, and (3) the mental representations constructed throughout the reuse activity, e.g. dynamic versus static representations. Some implications of these results for the specification of software reuse support environments are discussed.