27376484
Monitoring Behavior in Manual and Automated Scheduling Systems
Abstract Human monitoring behavior in manual and automated scheduling systems is examined through an experiment that required the subjects to perform scheduling and monitoring tasks. The task required the assignment of a series of incoming customers to the shortest of three parallel service lines. The subject was either in charge of the customer assignment (Manual Mode) or was monitoring an automated system performing the same task (Automatic Mode). In both cases, the subjects were required to detect the nonoptimal assignments that they or the computer had made. The results showed better error detection performance and lower subjective workload in the automatic mode. The subjects in the manual mode were both biased against declaring their own assignment errors and less sensitive to their misassignments. Results are compared with previous findings of monitoring behavior in manual control systems, and are discussed in terms of human decision making, reliability, workload and system design.
8252393
Queueing Network-Model Human Processor (QN-MHP): A computational architecture for multitask performance in human-machine systems
Queueing Network-Model Human Processor (QN-MHP) is a computational architecture that integrates two complementary approaches to cognitive modeling: the queueing network approach and the symbolic approach (exemplified by the MHP/GOMS family of models, ACT-R, EPIC, and SOAR). Queueing networks are particularly suited for modeling parallel activities and complex structures. Symbolic models have particular strength in generating a person's actions in specific task situations. By integrating the two approaches, QN-MHP offers an architecture for mathematical modeling and real-time generation of concurrent activities in a truly concurrent manner. QN-MHP expands the three discrete serial stages of MHP, of perceptual, cognitive, and motor processing, into three continuous-transmission subnetworks of servers, each performing distinct psychological functions specified with a GOMS-style language. Multitask performance emerges as the behavior of multiple streams of information flowing through a network, with no need to devise complex, task-specific procedures to either interleave production rules into a serial program (ACT-R), or for an executive process to interactively control task processes (EPIC). Using QN-MHP, a driver performance model was created and interfaced with a driving simulator to perform a vehicle steering, and a map reading task concurrently and in real time. The performance data of the model are similar to human subjects performing the same tasks.
9965299
Computational modeling and experimental investigation of effects of compositional elements on interface and design aesthetics
This article describes computational modeling and two corresponding experimental investigations of the effects of symmetry, balance and quantity of construction elements on interface aesthetic judgments. In the first experiment, 30 black and white geometric images were developed by systematically varying these three attributes in order to validate computational aesthetic quantification algorithms with subject ratings. The second experiment employed the same image layout as Experiment 1 but with realistic looking web pages as stimuli. The images were rated by 16 subjects in each experiment using the ratio-scale magnitude estimation method against a benchmark image with average balance and symmetry values and a standard number of elements. Subjects also established an ordered list of the images according to their aesthetic appeal using the Balanced-Incomplete-Block (BIB) ranking method. Results from both experiments show that subjects are adept at judging symmetry and balance in both the horizontal and vertical directions and thus the quantification of those attributes is justified. The first experiment establishes a relationship between a higher symmetry value and aesthetic appeal for the basic imagery showing that subjects preferred symmetric over non-symmetric images. The second experiment illustrates that increasing the number of groups in a web page causes a decrease in the aesthetic appeal rating.
15475945
Performance prediction of component-based applications
One of the major problems in building large-scale enterprise systems is anticipating the performance of the eventual solution before it has been built. The fundamental software engineering problem becomes more difficult when the systems are built on component technology. This paper investigates the feasibility of providing a practical solution to this problem. An empirical approach is proposed to determine the performance characteristics of component-based applications by benchmarking and profiling. Based on observation, a model is constructed to act as a performance predictor for a class of applications based on the specific component technology. The performance model derived from empirical measures is necessary to make the problem tractable and the results relevant. A case study applies the performance model to an application prototype implemented by two component infrastructures: CORBA and J2EE.
14300663
Performance Model for a Prioritized Multiple-Bus Multiprocessor System
The performance of a shared memory multiprocessor system with a multiple-bus interconnection network is studied in this paper. The effect of bus and memory contention is modeled using a probabilistic model and a closed form solution for the acceptance probability of each processor is presented. It is assumed that each processor in the system has a distinct priority assigned to it and that arbitration is based on priority. Whenever a request from a processor is rejected due to bus or memory conflicts, the request is resubmitted until granted. Based on the model, individual processor acceptance probabilities are first estimated, from which the effective memory bandwidth is computed. The accuracy of the analytical model is verified based on simulation results. Results from the model are compared against other approximate models previously reported in literature. It is observed that the inaccuracy of the model measured in terms of error from simulation results is less than that in previously reported studies.
912445
Efficient Symbolic Detection of Global Properties in Distributed Systems
A new approach is presented for detecting whether a computation of an asynchronous distributed system satisfies Poss Φ (read “possibly Φ”), meaning the system could have passed through a global state satisfying property Φ. Previous general-purpose algorithms for this problem explicitly enumerate the set of global states through which the system could have passed during the computation. The new approach is to represent this set symbolically, in particular, using ordered binary decision diagrams. We describe an implementation of this approach, suitable for off-line detection of properties, and compare its performance to the enumeration-based algorithm of Alagar & Venkatesan. In typical cases, the new algorithm is significantly faster. We have measured over 400-fold speedup in some cases.
14808044
Fast Evolutionary Programming
Evolutionary programming (EP) has been applied to many numerical and combinatorial optimisation problems successfully in recent years. One disadvantage of EP is its slow convergence to a good near optimum for some function optimisation problems. In this paper, we propose a fast EP (FEP) which uses a Cauchy instead of Gaussian mutation operator as the primary search operator. The relationship between FEP and classical EP (CEP) is similar to that between the fast simulated annealing and the classical version. Extensive empirical studies have been carried out to evaluate the performance of FEP for diierent function optimisation problems. Fifty runs have been conducted for each of the 23 test functions in our studies. Our experimental results show that FEP performs much better than CEP for multi-modal functions with many local minima while being comparable to CEP in performance for unimodal and multi-modal functions with only a few local minima. We emphasise in the paper that no single algorithm can be the best for all problems. What we need is to identify the relationship between an algorithm and a class of problems which are most amenable to the algorithm.
14275207
The Architectural Design of FRUIT: A Family of Retargetable User Interface Tools
Forms-based user interfaces are widely used means for human-computer interaction. However, it is difficult to exploit software reuse in forms-based systems because the systems tend to be dependent upon the particular display technologies used. This paper introduces the Family of Retargetable User Interface Tools (FRUIT) that aims to solve this problem. FRUIT adapts the device-independent XForms technology to deliver a family of products capable of supporting a variety of display technologies. This paper presents the architecture for the FRUIT product line and illustrates the design methodology used—a methodology based on stepwise refinement and commonality and variability analysis; it also describes two members of the FRUIT family and shows how their designs and implementations are refinements of the family architecture.