Using GOMS to predict the usability of user interfaces of small off-the-shelf software products

The design of user interfaces and how usable they are, are both important research topics in computer science. This thesis is a research effort aimed at exploring the whole concept of usability and measuring the quality of a user interface in terms of how usable it is. Usability means how easy a system can be learned and used. In order to have usable products, they must be initially designed with usability in mind. A survey of methods for designing user interfaces which incorporate usability are outlined and they include some or all of the principles for designing for usability, proposed by various authors. Evaluating the quality of existing interfaces can be done by various methods.The method used in this dissertation is the GOMS (goals, operators, methods and selection rules) approach. This model was initially proposed by [Card, Moran & Newell 83] and the approach is based on constructing an explicit model of the user's procedural knowledge, entailed by a particular system design. [Kieras & Poison 85] expanded this model to suggest that quantitive measures defined on this explicit representation of the user's knowledge can predict important aspects of usability. The predictions are obtained from a computer simulation model of the user's procedural knowledge that can actually execute the same tasks as the user. To test the reliability and accuracy of the GOMS model predictions, the author carried out a pseudo-experiment on four inexperienced users using two different types of word-processors. The actual results from the experiment were compared with the GOMS predictions.The GOMS model was found to have some limitations and some enhancements to the approach are proposed. It was also found that the experiment had some limitations and improvements for a better experiment are proposed

The application of natural language pragmatics in human-computer interaction.

The general aim of the work reported in this thesis is to investigate the viability of applying theories and principles from the field of natural language pragmatics to that of human-computer interaction. In pursuing this aim, the research falls broadly into three phases.The first of these is the exploitation and adaptation of the Gricean Cooperative Principle, its maxims and inferential rules to situations of computer use which do not employ natural language as the medium of communication. The purpose of this endeavour is to provide a novel and revealing analysis of non natural language interaction and to establish principles for dialogue design, the application of which enhance the quality of communication between system and user in such situations.The second phase concerns the application of the adapted Gricean principles to the design of a dialogue management system, intended to address some of the problems which other research has revealed users to experience in using the standard UNIX shell interface. This second phase resulted in the production of the QDOS system, which is both a simulation of part of the UNIX file system and an implementation of the proposed dialogue management system.This software acts as the vehicle for all subsequent evaluative exercises constituting the third phase. This takes the form of an evaluation of the QDOS system and its theoretical underpinning, based on a two-condition experiment and a protocol analysis, involving a number of experimental subjects.This research provides an original application of the Gricean Cooperative Principle in human-computer interaction and a theoretical and practical demonstration of the validity of this endeavour. It also adduces an analysis of the UNIX interface and its vagaries in terms of a principled and consistent set of criteria as well as identifying a significant class of dialogue breakdown, the circumstances and incidence of which cut across issues of interface style