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An Assessment of SEES Based on Operational Experiences
No full textDuring the Fall of 1995 a modified form of SEES (Software Engineering Evaluation System), denoted SEES, was defined and used in a study to examine the value added of Independent Verification and Validation. A follow-on study, and topic of this report, focuses on an assessment of SEES based on operational experiences gained from the 1995 study. The report partitions its findings relative to phases of the software development process
The User-Reported Critical Incident Method at a Glance
No full textThe over-arching goal of this work is to discuss the user-reported critical incident method, a cost-effective remote usability evaluation method for real-world applications involving real users, doing real tasks in real work environments. Several methods have been developed for conducting usability evaluation without direct observation of a user by an evaluator. However, contrary to the user-reported critical incident method, none of the existing remote evaluation methods (nor even traditional laboratory-based evaluation) meets all the following criteria: - data are centered around critical incidents that occur during task performance; - tasks are performed by real users; - users are located in normal working environment; - users self-report own critical incidents; - data are captured in day-to-day task situations; - no direct interaction is needed between user and evaluator during an evaluation session; - there is a cost-effective way to capture data; and - data are high quality and therefore relatively easy to convert into usability problems
Sluice: A Java-Based Framework for Collaborative Interactive Modular Visualization Environments
No full textWe present Sluice, a framework for constructing collaborative, interactive, modular visualization environments (CIMVEs) for use on the World Wide Web. Sluice supports using Java to build modules that create, manipulate, and generate visualizations of tables of data. Sluice provides necessary infrastructure for a CIMV, including interface specifications for methods that modules of the MVE must implement, event propagation to support interaction and dynamic updating, and mechanisms for efficiently supporting collaboration. Our fundamental description of data comes in the form of table which is filtered, extended, or otherwise manipulated to produce a new "view" of the data at each module. We use the observer/observable design pattern to support dynamic updating of visualizations downstream in the dataflow network. Sluice also supports on-the-fly manipulation of the dataflow network. Sluice uses functionality provided by the JavaBeans package to support introspection of modules. This allows CIMVE implementations to discover, query, and set the values of properties of modules at runtime. After describing the design rationale, capabilities, and implementation of Sluice, we then describe our prototype CIMVE named SIEVE
Subsequence and Run Heuristics for Sorting by Transpositions
No full textSorting by tranpositions is the problem of finding the minimum number of transpositions required to sort a permutation pi. A transposition involves repositioning a contiguous sequence (block) of elements by inserting it elsewhere in the permutation. The problem has applications in the study of genome rearrangements and phylogeny reconstruction. In this paper, several heuristics based on analyses of subsequences and runs in a permutation are employed. Experimental results are provided. The algorithm based on the longest increasing subsequence in a permutation appears most promising
Characterizing World Wide Web Queries
No full textLocating information on the WWW is a major activity for users, and Web Information Retrieval Systems (IRS) are becoming more important to support their endeavors. In this paper we characterize queries performed by Web users to such systems and give distributions for accesses to different Web IRS. We characterize clients' accesses, queries and user sessions. Our purpose is to reduce network and bandwidth by identifying ways to optimize interactions with the Web. We characterize clients' sessions by a sequence of Browsing, Searching, and Next steps, and demonstrate that more search steps correlate with a reduction in the number of bytes transferred
Modeling Correlated Proxy Web Traffic Using Fourier Analysis
No full textWe analyze the arrival rate of accesses to Web proxy caching servers. The results show that the data display strong periodic autocorrelation. The examined data sets show a consistent behavior in terms of having periods corresponding to daily and weekly cycles that can be explained in terms of daily and weekly cyclic behavior of Web users. While these results confirm the correlation in the network traffic noticed by other researchers, we emphasize that this correlation is periodic. A new approach is introduced to model data that exhibit such characteristics by a combination of Fourier and statistical analysis techniques. The source of high correlation in the data is shown to come from the periodic and hence the deterministic part. Synthesized data that results from this modeling approach is shown to have a long-range dependent and self-similar behavior
Parallel Cost Analysis of Adaptive GMRES Implementations for Homotopy Methods
No full textThe success of homotopy methods in solving large-scale optimization problems and nonlinear systems of equations depends heavily on the solution of large sparse nonsymmetric linear systems on parallel architectures. Iterative solution techniques, such as GMRES(k), favor parallel implementations. However, their straightforward parallelization usually leads to a poor parallel performance because of global communication incurred by processors. One variation on GMRES(k) considered here is to adapt the restart value k for any given problem and use Householder reflections in the orthogonalization phase to achieve high accuracy and to reduce the communication overhead. The Householder transformations can be performed without global communications and modified to utilize an arbitrary row distribution of the coefficient matrix. The effect of this modification on the GMRES(k) performance is discussed here, as well as the abilities of parallel GMRES implementations using Householder reflections to maintain fixed efficiency with increase in problem size and number of processors. Theoretical communication cost and isoefficiency analyses are compared with experimental results on an Intel Paragon, Gray T3E, and IBM SP2
An Empirical Study of Reuse, Quality, and Productivity
No full textThis paper presents an analysis of four sets of industrial data to determine if software reuse is correlated with higher levels of software quality and productivity
Using Belbin's Role to Improve Team Effectiveness
No full textThis paper presents a controlled experiment conducted with software engineering students that demonstrates the utility of forming teams based on R. Meredith Belbin's set of team roles. The overall research effort is a demonstration of the general utility of Belbin's roles in improving the effectiveness of teams, even industry teams. The significance of this work is twofold: performance and team viability. Performance improvements clearly improve a team's productivity; viability issues are important because if employees remain with a team or employer, then employee replacement costs are reduced. To address this problem, as an initial step, controlled experiments have been conducted to demonstrate that teams that contain certain roles perform better than teams that do not. In a laboratory setting, a number of teams were formed that contained a single leader; other teams were formed that had no leader or multiple leaders. The results of this single experiment are positive. They demonstrate that indeed Belbin's roles are useful knowledge in forming teams. The specific conclusion of this first controlled experiment is that a single leader on a team perform better than having multiple leaders or no leader. In other words, as one would expect, the mean time to completion for the leaderless group of teams was significantly larger than the group of teams with leaders. This means that Belbin's roles can be utilized in team formation, making sure that a team has a single leader, and also for evaluation on extant teams. Both of these aspects, formation and evaluation, are extremely useful to managers of software programmers
Sparse Approximate Inverses in Preconditioning Distributed Linear Systems
No full textUsing a direct approximation of sparse matrix inverse in preconditioning is viewed as a good alternative to the preconditioning techniques that require a matrix factorization. A sparse approximate inverse is easy to compute and apply, and it is suitable for parallel implementations. For distributed linear systems of varying difficulty, approximate block LU preconditioning using sparse approximate inverse techniques and an incomplete LU factorization used in Block-Jacobi preconditioning are compared