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The purpose of this research was to provide evidence to support specific features of a software user interface implementation. A 3 x 2 x 2 full factorial, between subjects design was employed, in a laboratory experiment systematically varying existence or non-existence of a user interface and media of help documentation (either online or written), while blocking for varying levels of user experience. Subjects completed a set of tasks using a computer, so the experimenters could collect and evaluate various performance and attitudinal measures. Several attitudinal measures were developed and validated as part of this research. Consistent with previous findings, this research found that a user's previous level of experience in using a computer had a significant impact on their performance measures. Specifically, increased levels of user experience were associated with reduced time to complete the tasks, fewer number of characters typed, fewer references to help documentation, and fewer requests for human assistance. In addition, increased levels of user experience were generally associated with higher levels of attitudinal measures (general attitude toward computers and satisfaction with their experiment performance). The existence of a user interface had a positive impact on task performance across all levels of user experience. Although experienced users were not more satisfied with the user interface than without it, their performance was better. This contrasts with at least some previous findings that suggest experienced users are more efficient without a menu-driven user interface. The use of online documentation, as opposed to written, had a significant negative impact on task performance. Specifically, users required more time, made more references to the help documentation, and required more human assistance. However, these users generally indicated attitudinal measures (satisfied) that were as high with online as written documentation. There was a strong interaction between the user interface and online documentation for the task performance measures. This research concludes that a set of tasks can be performed in significantly less time when online documentation is facilitated by the presence of a user interface. Written documentation users seemed to perform equivalently with or without the user interface. With online documentation the user interface became crucial to task performance. Research implications are presented for practitioners, designers and researchers.

This dissertation is concerned with the design of a generic gateway which provides an interoperability between dissimilar computer networks. The generic gateway is decomposed with subnetwork dependent blocks and subnetwork independent blocks. The subnetwork dependent block is responsible to communicate with subnetwork nodes. The subnetwork independent block is responsible to interconnect the subnetwork dependent blocks. The communications between subnetwork dependent and independent blocks are done by service access points which defined independently to any specific subnetworks. Formal specification of a generic gateway is provided by LOTOS. The generic gateway specification is tested by a verifiable test method which is proposed in this dissertation. The correctness of the specification has been verified while the specified model is simulated. The major difference between conventional simulation and the verifiable test is in the objective of simulation. In the verifiable test method, the semantical properties are examined during the simulation process. The tester can be either human observer or other process.

Current research in screen design for human computer interaction has demonstrated that user task performance is influenced by placement, prompting methodology, and screen complexity. To assess the difference between a grouped item screen prompt and a series of single item screen prompts, a field experiment in a semiconductor manufacturing facility was designed. Subjects were randomly assigned to one of two groups to use a data entry system. Seven of the screen prompts differed between the two groups. During the four weeks of the study, a significant difference was measured between groups. The group screen users had lower task times for all four weeks. No significant correlation exists between work experience, performance review scores, or designated work shift. A strong negative correlation exists between frequency of system usage and task time. No difference was noted for measured errors. Subjective scores significantly favored the group screen design.

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