Richard Butterworth

Demonstrating the cognitive plausibility of interactive system specifications

Abstract. Much of the behaviour of an interactive system is determined by its user population. This paper describes how assumptions about the user can be brought into system models in order to reason about their behaviour. We describe a system model containing reasonable assumptions about the user as being ‘cognitively plausible’. Before asserting the plausibility of a model however we must first be able to make the assumptions made in that model inspectable.There is a tension between the inspectability of user assumptions and the tractability of models; inspectable models tend to not be very tractable and vice versa. We describe how we can get round this tension, by deriving tractable models from explicit user assumptions. The resulting models may not of themselves be very inspectable to human-factors workers, but the process by which they are derived is inspectable. Hence we claim that we can have both tractability and inspectability. We exemplify our claims using a simple cognitive model and ‘Meeting Maker’, an interactive electronic diary system.

Users as rational interacting agents: formalising assumptions about cognition and interaction

One way of assessing the usability of a computer system is to make reasonable assumptions about users’ cognition and to analyse how they can be expected to work with the system, using their knowledge and information from the display to achieve their goals. This is the approach taken in Programmable User Modelling Analysis, a technique for predictive usability evaluation of interactive systems. The technique is based on the premise that an analyst can gain insights into the usability of a computer system by specifying the knowledge that a user needs to be able to use it and drawing inferences on how that knowledge will guide the user’s behaviour. This may be done by observing how a cognitive architecture, “programmed” with that knowledge, behaves. An alternative approach is to develop a formal description of the essential features of the cognitive architecture and to use that description to reason about likely user behaviour. In this paper, we present the approach and an outline formal description of the cognitive architecture. This initial description is derived from an existing implementation. We illustrate how the description can be used in reasoning by applying it to the task of setting up call diverting on a mobile phone. Successful performance of this task involves a combination of planned and responsive behaviour. The process of doing this analysis highlights what assumptions have been made by the designers about the user’s knowledge. We discuss limitations of the current formalisation and identify directions for future work.

Disrupting digital library development with scenario informed design

In recent years, there has been great interest in scenario-based design and other forms of user-centred design. However, there are many design processes that, often for good reason, remain technology-centred. We present a case study of introducing scenarios into two digital library development processes. This was found to disrupt established patterns of working and to bring together conflicting value systems. In particular, the human factors approach of identifying users and anticipating what they are likely to do with a system (and what problems they might encounter) did not sit well with a development culture in which the rapid generation and informal evaluation of possible solutions (that are technically feasible and compatible with stable system components) is the norm. We found that developers tended to think in terms of two kinds of user: one who was exploring the system with no particular goal in mind and one who knew as much as the developer; scenarios typically work with richer user descriptions that challenge that thinking. In addition, the development practice of breaking down the design problem into discrete functions to make it manageable does not fit well with a scenario-based approach to thinking about user behaviour and interactions. The compromise reached was scenario-informed design, whereby scenarios were generated to support reasoning about the use of selected functions within the system. These scenarios helped create productive common ground between perspectives.

Using Formal Models to Explore Display-Based Usability Issues

This paper addresses how user assumptions can be expressed mathematically so that they can be integrated with an abstract device model. Such an integrated model allows usability decisions to be made about abstract system models to complement the more traditional approach of usability evaluation by user testing.In particular, we address the question of what knowledge the user requires in order to successfully achieve a given task and the role the display plays in supplying and maintaining that knowledge. We illustrate our approach using a modelled web browser.We present two abstract models of the display and discuss how these differing designs affect user knowledge and therefore behaviour. We expose an apparently paradoxical result: that improving the user knowledge about the device may lead to more error-prone behaviour. This result leads us to a discussion of what it actually means (and does not mean) for a device to be `usable?.

The Role of Formal Proof in Modelling Interactive Behaviour.

When proving properties of formally described interactive systems, trade-offs have to be made between the simplicity of the model — which relates to the ease of performing proofs — and the real-world validity of the model. This issue is particularly important when the proof incorporates properties of user behaviour as well as the device specification. This paper discusses these trade-offs, using a simple model of a web-browsing system as an example. The property we focus on relates to usability: showing whether or not the things a user wants to do are easy to do.

Using the information seeking and retrieval framework to analyse non-professional information use

The outcomes of three digital library projects are discussed within Ingwersen and Järvelins Information Seeking and Retrieval framework [1]. The common theme of these projects is that they addressed information use by users who were neither academics or information professionals. This generates a picture of information use not often seen in the LIS literature, and shows some interesting differences between professional and non-professional information use, particularly in the areas of organisational and social context. The value of Ingwersen and Järvelins framework is shown in that it promotes the identification of commonalities between the different projects, promotes explanations of some of the observations made in the three projects, and suggests an agenda for future work.

Assessing the roles that a small specialist library plays to guide the development of a hybrid digital library

A case study of the development of a hybrid digital library system for a small, specialist library is discussed. It is proposed that small, specialist libraries play different roles for their stakeholders than academic or commercial libraries do, and therefore different models of digital library systems are required. It is primarily shown that the community building and supporting roles are much stronger and more important and that financial resources are even more scarce than for academic and commercial libraries. Although the findings are based on an in-depth analysis of one library, a semi-formal interview study with librarians from similar institutions was undertaken. This demonstrates that the arguments presented here have a good level of generality.

Expeditions through image jungles The commercial use of image libraries in an online environment

Purpose – Searching for appropriate images as part of a work task is a non-trivial problem. Journalists and copywriters need to find images that are not only visually appropriate to accompany the documents they are creating, but are acceptably priced and licensed. The paper aims to discuss these issues. Design/methodology/approach – A work-based study methodology and grounded theory are used to collect qualitative data from a variety of creative professionals including journalists. Findings – The authors report the findings of a study to investigate image search, retrieval and use by creative professionals who routinely use images as part of their work in an online environment. The authors describe the commercial constraints that have an impact on the image users’ behaviour that are not reported in other more academic and lab-based studies of image use (Westman, 2009). Practical implications – The authors show that the commercial image retrieval systems are based on document retrieval systems, and that th...

On biasing behaviour to the optimal

A formal framework for synthesizing interactive systems is outlined. A distinction is made between the functional ‘behaviour’ of a system, which is a description of everything that the user is permitted to do, and the ‘use’ of a system, which is what the user is likely to do. A way for capturing the use requirements of a system in terms of how ‘good’ is a given use is proposed and discussed as well as a way of describing interface specifications and terms of what user interfaces do rather than how they do it. The two aspects are related so that an analyst can judge whether changes in the interface model cause required improvements in the use of the system. Some of the implications of this approach are discussed and a comparison is made to other formal approaches in HCI.

Social Tagging: Exploring the Image, the Tags, and the Game

An increasing amount of images are being uploaded, shared, and retrieved on the Web. These large image collections need to be properly stored, organized and easily retrieved. Tags have a key role in image retrieval but it is difficult for those who upload the images to also undertake the quality tag assignment for potential future retrieval by others. Relying on professional keyword assignment is not a practical option for large image collections due to resource constraints. Although a number of content-based image retrieval systems have been launched, they have not demonstrated sufficient utility on large-scale image sources on the web, and are usually used as a supplement to existing text-based image retrieval systems. An alternative to professional image indexing can be social tagging -- with two major types being photo-sharing networks and image labeling games. Here we analyze these applications to evaluate their usefulness from the semantic point of view. We also investigate whether social tagging behaviour can be managed. The findings of the study have shown that social tagging can generate a sizeable number of tags that can be classified as interpretive for an image, and that tagging behaviour has a manageable and adjustable nature depending on tagging guidelines.