12496489
Studying long-term system use
here have been many studies of computer users but few that extend over very long periods. The reasons for this include costs, the quality of the data that can be obtained and satisfactorily analyzed , and the requirement to obtain results in the short term. We were interested in building long-term user models for teaching systems and wished to track the total development of a guru as well as other types of users. Such goals require tracking large numbers of people over a very long period, because guru-level experience takes years to acquire, and it cannot be predicted in advance who will turn out to develop this level of skill. Therefore, to find even one guru may require the tracking of around 20 to 100 users for a year or two. Finding 10 gurus might require 1,000 users. It is possible to observe such numbers over years only by using a method that is very careful about costs. The objective of this article is to present a methodology for monitoring many users in their natural settings over the long term and to give an example of its application to the domain of students learning an editor for three years. We show how data obtained from this methodology permits the construction of individual user models. Monitoring Methodology We developed a monitoring system to study the use of the sam text editor [13]. It is essentially a modeless editor, with most basic commands invoked using the mouse. It also has powerful keyboard commands, issued through the command window, including the usual Unix regular expressions and an elegant interface to the Unix shell. We had a number of design goals for our system, which strongly influenced our methods. First, we were restricted to low system-building costs followed by very low operational costs. Second, the system needed to be highly reliable; it would not be possible to make changes once the monitoring was under way, nor could the immediate availability of people to fix problems during operation be guaranteed. Third, the impact on the computing resources had to be negligible-a degradation in performance during the day was not an option. Fourth, we wanted to give the users some control over their own data, they should be able to read it and delete it if they really wanted. Finally, and most demandingly, we wanted to measure the time of first use of each command, but …
36594745
A Distributed Usage Monitoring System
We are developing a distributed computer system that supports usability and interaction studies, by handling the collection, storage and analysis of usage data, such as that generated by user-computer interaction and associated sensing devices (e.g., cameras). Data sources may be distributed as may be the data repositories and data consumers (other computer processes and human investigators). The system supports dynamic configuration of the entire process, including changes in the goals of the investigation itself. In this paper we describe the system’s key features, including a generic and evolvable data transport and processing network, a set of tools for capturing and cleaning usage data, a tool for instrumenting software for data capture, and a system for managing the entire process. We also report on several trials of the system, identifying successes, failures, lessons learned and areas for future development.
1883056
An Investigation into Keystroke Latency Metrics as an Indicator of Programming Performance
Typing has long been studied in psychology and HCI, and strong cognitive models for transcription typing exist. The goal of the present research was to test if there is any correlation between students' keystroking speed and performance while they are programming. We present the results from two studies with computer science students conducted in different contexts. Keystroke timings were recorded while they worked on Java and Ada source code. Quality of their programming work was measured mainly in terms of completeness. In the controlled experiment that lasted six hours, 39 students undertook three change tasks on a 6000 LOC Java application. In the field study, data was collected over 6 weeks from 141 students while they worked unsupervised on Ada programming in first year laboratories. In both cases there were highly significant (P=0.001), moderately strong, negative correlations between speed and coding performance. With additional development, these techniques may have promise for user modelling and assessment as well as in educational diagnostics.
14742276
Finger tracking for the Digital Desk
One trend in computing environments today is to move towards more 'natural' interaction. Another is to make hardware invisible to the user. Both these ideas converge into ubiquitous computing-the Digital Desk is an example of this idea. In this paper, we concentrate on an input device for the Digital Desk, namely the user's fingertip, which is made to act like a mouse. Tracking such an input device is common to a number of augmented reality environments and involves vision and motion analysis. However, previous attempts have focused more on the vision aspect of tracking general objects than on using the information already known about the user's hand, which is the approach taken in this paper. We adopted the goal of tracking the user's fingertips as fast as possible in real time, so that the system could be compared with other input devices by using models such as Fitts' law. Our system is shown to comply with the law adequately.
9403384
A pilot study of teaching the strategic use of common computer applications
Many users do not progress from a basic use of computer applications to more efficient usage. A strategic approach to training that focuses on teaching efficient strategies in addition to commands was successfully developed by Bhavnani and John at Carnegie Mellon University. A controlled experiment comparing this method of teaching to traditional command-based instruction was performed at the University of Western Australia. We found the teaching method is transferable to the Australian context and it appears to be remarkably robust in terms of delivery, student prior experience levels and motivation. The results clearly indicate that students can be taught to use common computer applications more efficiently than they would otherwise achieve.
13952604
Generating Internally Four-Connected Graphs
A graph is a minor of another if the first can be obtained from a subgraph of the second by contracting edges. A graph G is internally 4-connected if it is simple, 3-connected, has at least five vertices, and if for every partition (A, B) of the edge-set of G, either |A|?3 or |B|?3 or at least four vertices of G are incident with an edge in A and an edge in B. We prove that if H and G are internally 4-connected graphs such that they are not isomorphic, H is a minor of G, and they do not belong to a family of exceptional graphs, then there exists a graph H? such that H? is isomorphic to a minor of G and either H? is obtained from H by splitting a vertex or H? is an internally 4-connected graph obtained from H by means of one of four possible constructions. This is a first step toward a more comprehensive theorem along the same lines.
206570506
Quickly Excluding a Planar Graph
Abstract In an earlier paper, the first two authors proved that for any planar graph H , every graph with no minor isomorphic to H has bounded tree width; but the bound given there was enormous. Here we prove a much better bound. We also improve the best known bound on the tree-width of planar graphs with no minor isomorphic to a g × g grid.
2645465
Algorithms Finding Tree-Decompositions of Graphs
Abstract A graph G has tree-width at most w if it admits a tree-decomposition of width ≤ w . It is known that once we have a tree-decomposition of a graph G of bounded width, many NP-hard problems can be solved for G in linear time. For w ≤ 3 we give a linear time algorithm for finding such a decomposition and for a general fixed w we obtain a probabilistic algorithm with execution time O ( n log 2 n + n log n ∥log p ∥), which for a graph G on n vertices and a real number p > 0 either finds a tree-decomposition of width ≤ 6 w or answers that the tree-width of G is ≥ w ; this second answer may be wrong but with probability at most p . The second result is based on a separator technique which may be of independent interest.
37344904
Power System Bidding Tournaments for a Deregulated Environment
In this paper we describe certain tools for understanding and operating power systems in a deregulated environment. Many of the current models for this competitive market that employ an independent system operator (ISO) for controlling transmission, ensuring fair access and security, and providing a spot market for power will be studied. This centrally-dispatched power pool also ensures that generation meets demand based on bids submitted daily from independent generators (and from customers offering interruptible loads). Currently, most I S 0 bidding models allow only a single bid per day. In this paper, we present an asynchronous bidding scheme as a possible alternative. In particular, we examine the effects of including a feedback mechanism such that upon receiving generation levels from the ISO, independent generators (IGs) be allowed to modify their bid if they so desire. This competitive or ‘sequential’ bidding process should be allowed to take place each day for a predetermined period of time; in this way, IGs will have a chance to compete and hopefully optimize their profit margins. This paper also discusses the development tools necessary for examining the effects of different bidding processes on the I S 0 model and evaluating their capability of driving the market to an efJicient state of operation.
14962541
Efficiently four-coloring planar graphs
An outline of aquadratic algorithm to 4-color planar graphs is presented, based upon anew proof of the Four Color Theorem. This algorithm improves aquartic algorithm of Appel and Haken.