Thomas R. G. Green

• University of York

Notations develop over time. We propose that they characteristically pass through a series of development stages, starting very simple and becoming more complex, reaching a stage of complexity that hinders their usability: then, often, a new higher-level notation is developed that is once again simple, and will perhaps pass through the same develop...

Computer programming could be made easier. This paper gives a short account of the authors' empirical studies of programming, showing that very considerable improvements can be obtained both for beginners and for professionals. The improvements are related to, though not wholly dependent on, the new concepts of ‘structured programming’; we have fou...

Programming languages embody two principal forms of conditional statement, the nesting if … then … else … form and the goto form. Sime, Green & Guest (1974) compared these two and a third variety not in common use, nesting with redundancy, and they found that non-programmers learning to write programs based on conditionals obtained best results wit...

A measure is described which attempts to quantify one aspect of search behaviour, namely, the frequency of referring back to earlier parts of the search pattern or ‘harking back’. In a dialogue, harking back corresponds to bringing a topic up again when it was mentioned earlier; in a problem-solving task, it corresponds to putting aside one line an...

Analytical usability evaluation methods (UEMs) can complement empirical evaluation of systems: for example, they can often be used earlier in design and can provide accounts of why users might experience difficulties, as well as what those difficulties are. However, their properties and value are only partially understood. One way to improve our un...

There is a wealth of user-centred evaluation methods (UEMs) to support the analyst in assessing interactive systems. Many of these support detailed aspects of use—for example: is the feedback helpful? Are labels appropriate? Is the task structure optimal? Few UEMs encourage the analyst to step back and consider how well a system supports users’ con...

Many systems form ‘chains’ whereby developers use one system (or ‘tool’) to create another system, for use by other people. For example, a web development tool is created by one development team then used by others to compose web pages for use by yet other people. Little work within Human-Computer Interaction (HCI) has considered how usability cons...

The cognitive dimensions framework has inspired research both more and less varied than expected. In this paper, we revisit the original aims and briefly describe some subsequent research, to consider whether the original aims were too austere in rejecting knowledge-based dimensions; whether the dimensions can be shown to have real-world relevance;...

Many of the difficulties users experience when working with interactive systems arise from misfits between the user’s conceptualisation of the domain and device with which they are working and the conceptualisation implemented within those systems. We report an analytical technique called CASSM (Concept-based Analysis for Surface and Structural Mis...

Concept-based Analysis of Surface and Structural Misfits (CASSM) in a novel approach to usability analysis that focuses attention on misfits between user and system concepts. We believe that as an approach it has several desirable qualities: o It focuses on concepts rather than tasks or procedures. Consequently, it complements the majority of exist...

We focus on the ability of two analytical usability evaluation methods (UEMs), namely CASSM (Concept-based Analysis for Surface and Structural Misfits) and Cognitive Walkthrough, to identify usability issues underlying the use made of two London Underground ticket vending machines. By setting both sets of issues against the observed interactions wi...

Children have problems in understanding and becoming proficient in abstract representational systems that convey concepts, such as algebra. We focus here on using diagrams to help them learn to translate arithmetic word problems into calculator expressions. The problem here is learning how to find a mapping between features of the word problems and...

This chapter provides information to notational systems that range from complex products, such as visual-programming languages, to embedded functionality, such as central-heating controls. Notational systems have four components: an interaction language or notation; an environment for editing the notation; a medium of interaction; and two kinds of...

Is it possible to achievesomeofthe benefits of formal testing within the informal programming conven tions of the spreadsheet paradigm? Wehave been working on an approach that attempts to do so via the developmentof a testing methodology for this paradigm. Our "What You See Is What You T est" (WYSIWYT) methodology supplements the conven tion bywhic...

Ontological Sketch Modelling (OSM) is a novel approach to usability evaluation that concentrates on both the user’s conceptual model of the domain and ‘working practices’, and the conceptual model built into a device or a work-system. Analysing the degree of fit between these models can reveal potential problems in learning and use that are not rev...

Visual programming languages aim to promote usability, but their usability is rarely examined scientifically. One reason is the difficulty of designing successful experimental evaluations. We propose the Cognitive Walkthrough (CW) as an aid to improve experiments' designs. The CW is an HCI technique designed for evaluating interfaces. The technique...

Visual programming languages aim to promote usability, but their usability is rarely examined scientifically. One reason is the difficulty of designing successful experimental evaluations. We propose the Cognitive Walkthrough (CW) as an aid to improve experiments' designs. The CW is an HCI technique designed for evaluating interfaces. The technique...

The Cognitive Dimensions of Notations framework has been created to assist the designers of notational systems and information artifacts to evaluate their designs with respect to the impact that they will have on the users of those designs. The framework emphasizes the design choices available to such designers, including characterization of the us...

Visual programming languages aim to promote usability, but are rarely examined for it. One reason is the difficulty of designing successful experimental evaluations. We propose the Cognitive Walkthrough as an aid to improve experimental designs. This is a novel application of an HCI-derived technique designed for evaluating interfaces rather than e...

Users working with documents that are too large and detailed to fit the user's screen (e.g. chip designs) have the choice of zooming or applying appropriate visualization techniques. In this demonstration, we will present focus plus context screens-wall-size ...

A novel usability evaluation technique, Ontological Sketch Modelling (OSM), was applied to the analysis of systems used within a complex work setting, namely emergency medical dispatch. OSM focuses on the structure of the domain in question and the devices which are applied to that domain, in order to reason about the quality of fit between the two...

Some studies of diaries and scheduling systems have considered how individuals use diaries with a view to proposing requirements for computerised time management tools. Others have focused on the criteria for success of group scheduling systems. Few have paid attention to how people use a battery of tools as an ensemble. This interview study report...

The Cognitive Dimensions of Notations framework has been created to assist the designers of notational systems and information artifacts to evaluate their designs with respect to the impact that they will have on the users of those designs. The framework emphasizes the design choices available to such designers, including characterization of the us...

The Cognitive Dimensions of Notations framework has been created to assist the designers of notational systems and information artifacts to evaluate their designs with respect to the impact that they will have on the users of those designs. The framework emphasizes the design choices available to such designers, including characterization of the us...

The Cognitive Dimensions framework outlined here is generalised broad-brush approach to usability evaluation for all types of information artifact, from programming languages through interactive systems to domestic devices. It also has promise of interfacing successfully with organisational and sociological analyses. Keywords Usability evaluation,...

This paper approaches music notation as one example of a more general class of notation systems. Our work on notation systems was originally motivated by the need to understand the factors affecting the usability of programming languages (Blackwell 1996, Green & Petre 1996). Since then we have considered an increasingly wide range of usability prob...

The Cognitive Dimensions of Notations framework (CDs) provides a powerful vocabulary for discussing the usability of programming languages, tools and environments. Although originally proposed as a discussion tool for designers, they have recently been used to design questionnaires intended for system users evaluating the usability of the programmi...

Data modelling reveals the internal structure of an information system, abstracting away from details of the physical representation. We show that entity-relationship modelling, a well-tried example of a data-modelling technique, can be applied to both interactive and non-interactive information artefacts in the domain of HCI. By extending the conv...

Is it possible to achieve some of the benefits of formal testing within the informal programming conventions of the spreadsheet paradigm? We have been working on an approach that attempts to do so via the development of a testing methodology for this paradigm. Our “What You See Is What You Test” (WYSIWYT) methodology supplements the convention by w...

Visual programming languages aim to promote usability, but are rarely examined for it. One reason is the difficulty of designing successful experimental evaluations. We propose the Cognitive Walkthrough as an aid to improve experimental designs. This is a novel application of an HCI-derived technique designed for evaluating interfaces rather than e...

There is a need for empirical evaluation of programming languages for unskilled users, but it is more effective to compare specific features common to many languages than to compare complete languages. This can be done by devising micro-languages stressing the feature of interest, together with a suitable subject matter for the programs. To illustr...

Previous research suggests that graphical metaphor should increase the usability of visual programming languages (VPLs) by providing an instructional aid when learning to use the language. This paper describes three experiments which manipulated the degree of metaphor in VPLs. In the first, an implicit pictorial metaphor was added to a dataflow lan...

We present a new visual programming language and environment that serves as a form of feedback and representation in a Programming by Demonstration system. The language di#ers from existing visual languages because it explicitly represents data objects and implicitly represents operations bychanges in data objects. The system was designed to provid...

this paper. Figure 2 - Instructions that might assist in defining a quick dial code

Previous research suggests that the graphical metaphor should increase the usability of visual programming languages (VPLs) by providing an instructional aid when learning to use the language. This paper describes three experiments which manipulated the degree of metaphor in VPLs. In the first, an implicit pictorial metaphor was added to a data flo...

There is a need for empirical evaluation of programming languages for unskilled users, but it is more effective to compare specific features common to many languages than to compare complete languages. This can be done by devising micro-languages stressing the feature of interest, together with a suitable subject matter for the programs. To illustr...

User interface development is concerned with producing computer-based systems and other ‘information artefacts’ that are effective and easy to learn and use for the intended users. During the process of developing user interfaces, the designer will need to produce a number of abstract representations, or models. There are a host of different modeli...

Ontological Sketch Modelling (OSM) is a novel approach to usability evaluation that uses entity analysis rather than detailed task analysis. Comparison of entity-based models of the domain as seen by the user and as supported by the device reveals misfits that cause usability problems; similarly, problems with the 'system image' can be exposed. In...

This chapter continues the theme of searching for information. It explores search that traverses many relationships. ERMIAs can be used to identify standard patterns which have standard characteristics for search.

This chapter continues the theme of searching for information. It describes the importance of searching for many-to-many relationships between entities.

The main aim of this chapter is to give you experience in developing ERMIAs. We look at three examples. In the first you will do most of the work. The second provides a detailed example of developing a perceptual ERMIA and the third of developing a large scale model of a conceptual ERMIA. As discussed in Chapter 9 ERMIAs take time to develop and ne...

This chapter aims to show how ERMIAs distinguish between the structure of the conceptual information that is contained in an information artefact, and the way that this information is made manifest to the user.

Information artefacts are built upon each other providing different levels of view onto the information and providing different types of view which reveal more or less of the underlying conceptual structure. In this chapter we examine the effect which these different views can have on helping or hindering users getting at the information they requi...

We have seen ERMIA in operation in a number of situations, mostly quite small systems. In this chapter we present a case study of ERMIA being used to evaluate a real and complex piece of software. Although the software is complex, and the domain will not be familiar to many readers, it is worth studying this chapter to get a feel for what ERMIA is...

This chapter introduces the problem of searching for information in an artefact. The aim of this chapter is to show how ERMIAs describe how the user can locate interesting individual entities, or groups of individuals with relevant properties, in an entity class. It presents ERMIA notation for how the entities in a class are stored and accessed.

Developing ERMIAs is something that takes practice. However, there are a number of useful “rules of thumb” which can help to guide the modeler. ERMIAs are also useful in focusing the discussions between different modelers. This chapter describes in detail the rules for building an ERMIA model.

Information artefacts need to be carefully designed so that they reveal the information which their users require This chapter provides an introduction to what ERMIA can do to help designers and choosers of information artefacts.

The aim of this chapter is to give a concise account of the elements of ERMIA diagrams. The formalism is explained and the main concepts are illustrated and discussed.

From the Publisher: Conceptual Modeling for User Interface Development provides a practical and usable technique for designing and evaluating user interfaces. The technique, called ERMIA, Entity-Relationship Modeling of Information Artefacts, has been developed with both the designers and the users of computer systems in mind, to provide a 'languag...

Cognitive Dimensions can be used for: evaluating usability or suggesting improvements. The dimensional approach helps elucidate the trade-offs inherent in different "design manouevers". A checklist can be constucted to ensure that an evaluative discussion has not overlooked certain points. When compared to traditiional approaches, CD differentiates...

This paper reports on the design and re-design of an Ontological Sketch Model. OSM is a representation and method of usability assessment that is based on descriptions of the device model and the user's conceptual model of that device. The ultimate aim of this work is to develop an approach that focuses attention on device and conceptual models, an...

The objective of the Visual Programming Challenge (VPC) is to focus the various visual programming approaches, both research and commercial, on a specific problem as a means of providing a comparative analysis. The competition domain is a problem involving quasi-real-time control of a robotic vehicle. The control of these robotic vehicles is repres...

An Ontological Sketch Model (OSM) is a structured but informal representation of the ontology --- the essential underlying structure --- of a system, forming a basis for usability assessment. Our primary aim is to develop an approach that is usable and that yields useful results. We present a preliminary ontology for the OSM, based on descriptions...

INTRODUCTION The analysis of tasks is a fundamental and important process in many areas of applied behavioural science. Task analysis offers methods for exploring relationships between the properties of systems and user performance. Traditionally (eg. see Miller, 1962), the analyst takes descriptions of the cues that should be perceived and the act...

Software visualization is nifty stuff; but is it the powerful cognitive tool it is often assumed to be? This chapter attempts to moderate the understandable enthusiasm for software visualization and to raise some of the questions for which the discipline doesn't yet have answers. The chapter is structured as a list of questions with discussion. The...

The cognitive dimensions framework is a broad-brush evaluation technique for interactive devices and for non-interactive notations. It sets out a small vocabulary of terms designed to capture the cognitively-relevant aspects of structure, and shows how they can be traded off against each other. The purpose of this paper is to propose the framework...

Data modelling reveals the internal structure of an information system, abstracting away from details of the physical representation. We show that entity-relationship modelling, a well-tried example of a data-modelling technique, can be applied to both interactive and noninteractive information artifacts in the domain of HCI. By extending the conve...

Although cognitive psychology showed much initial promise, it has failed to make significant contributions to the study of human-computer interaction, which has led to a rejection of cognitivism in favour of situated action theory. The authors accept that the critique has much to offer, but reject the outright abandoning of cognitivism. Cognitive p...

The theme of this paper is that simple comparisons between diagrams and text are inappropriate, at least in the programming area. Simple text-graphic comparisons are certainly very popular among computer scientists; we surveyed the literature and found that the vast majority made the simple assertion that visual programming would be better. Various...

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This paper reports a study of the use of card sorts in the categorisation of fragments of object-oriented programs. We are interested in the way in which programmer's think about code so that we might attempt to provide support for browsing and reuse within object-oriented environments. Hence, we have been exploring the use of knowledge acquisition...

The analytical tools of database modelling can be applied to information artefacts. We extend a well-known technique, entity-relationship modelling, to give models (‘structure maps’) of information structures in both static (paper-based) and interactive cases. Structure maps can reveal deep similarities between different-seeming devices, set bounds...

Spreadsheets and visual programming languages raise a challenge for exist- ing schema-based models of programming knowledge, which have been scarcely been ap- plied outside Pascal-like languages. Recent demonstrations of the role of mental imagery in spreadsheet programming raise another challenge to schema-based theories, which are propositional i...

Claims for the virtues of visual programming languages have generally been strong, simple-minded statements that visual programs are inherently better than textual ones. They have paid scant attention to previous empirical literature showing difficulties in comprehending visual programs. This paper reports comparisons between the comprehensibility...

: Spreadsheets and visual programming languages raise a challenge for existing schema-based models of programming knowledge, which have been scarcely been applied outside Pascal-like languages. Recent demonstrations of the role of mental imagery in spreadsheet programming raise another challenge to schema-based theories, which are propositional in...

Ten discretionary users were asked to recount their experiences with spreadsheets and to explain how one of their own sheets worked. The transcripts of the interviews are summarized to reveal the key strengths and weaknesses of the spreadsheet model. There are significant discrepancies between these findings and the opinions of experts expressed in...

This chapter centres on two observations. First,although software engineering environments are among the most interesting and enterprising products created by software engineers, they frequently contain features seen by psychologists and cognitive ergonomists as usability blunders. On the face of it, this problem stems directly from the second prob...

The call for participation for the Workshop on End User Programming began with the following statement:In the beginning, every user was a programmer. While that appeared to change forever in the 80's, the 90's are shaping up as the decade of macro-languages, scripting languages, authoring languages, dbase query languages, inter-application communic...

Understanding a program is easier when the visual representation of the program provides a 'cognitive map' conveying information about the program's structure and function. Although spreadsheets have been justly praised for improving on the presentation of conventional languages, programmers have much 'metacodistic' knowledge about the program that...

This paper suggests that experience influences what 'readers' of graphical representations look at and hence what they see, so that readership skills—both perceptual and interpretive—for graphical notations must be learned. It draws on results from two sets of empirical studies: observational studies of expert hardware designers using electronics s...

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Reports and analyzes claims made by 5 professional electronics designers about the notation of electronics and the computer-based design support systems they use, concentrating on cognitive issues of graphical representation. Seven themes emerged: overviews, zooming, neighborhood, shifts from graphics to text, viscosity, search trails, and vocabula...

Software engineers have developed sophisticated “object‐oriented” programming environments that are intended to make the reuse of program code easy. Experience has shown that these environments can be improved: Even very experienced programmers have problems in locating and comprehending code for reuse. Programs cannot be modified as readily as had...

This chapter describes three ‘implicit theories’ of programming, which have at different times governed the styles of programming language design. Not surprisingly, the experiments performed by empirical researchers have also been deeply influenced by the prevailing theory of the day. (1) The first view regarded programming as transcription from an...

(i) We first discuss educational objectives in teaching programming, using Logo research as a vehicle to report on versions of the ‘transfer of competence’ hypothesis. This hypothesis has received limited support in a detailed sense, but not in its original more grandiose conception of programming as a ‘mental gymnasium’. (ii) Difficulties in learn...