Corin A. Gurr

Effective Diagrammatic Communication: Syntactic, Semantic and Pragmatic Issues

The study of systems of communication may be divided into three parts: syntax, semantics and pragmatics. Accounts of the embedding of text-based languages in the computational processes of reasoners and communicators are relatively well developed, with accounts available for a spectrum of languages ranging from the highly formalised and constrained, such as formal logics, to the highly informal and unconstrained natural languages used in everyday conversations. Analogies between diagrams and such textual representations of information are quite revealing about similarities and differences and can provide a useful starting point for exploring the issues in a theory of diagrammatic communication. This paper sketches out a theory of diagrammatic communication, based upon recent studies of the syntactic, semantic and pragmatic component issues which such a theory must accommodate. In the context of this theory an exploration is made of the issues involved in answering the question: what makes for an effective diagrammatic representation? To achieve this we review a framework in which we may explore properties of representations, and properties of the relation between representations and that which they represent. By relating this framework to our sketched theory of diagrammatic communication, we explore the concept of effectiveness in diagrams. This process of exploration enables us to relate previous studies of the effectiveness of diagrams into a broader, unified framework, which clarifies both the various issues relating to effectiveness and the relations between them.

Cognitive Dimensions of Notations: Design Tools for Cognitive Technology

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 users activity, and the inevitable tradeoffs that will occur between potential design options. The resuliing framework has been under development for over 10 years, and now has an active community of researchers devoted to it. This paper first introduces Cognitive Dimensions. It then summarizes the current activity, especially the results of a one-day workshop devoted to Cognitive Dimensions in December 2000, and reviews the ways in which it applies to the field of Cognitive Technology.

Using Animation in Diagrammatic Theorem Proving

Diagrams have many uses in mathematics, one of the most ambitious of which is as a form of proof. The domain we consider is real analysis, where quantification issues are subtle but crucial. Computers offer new possibilities in diagrammatic reasoning, one of which is animation. Here we develop animated rules as a solution to problems of quantification. We show a simple application of this to constraint diagrams, and also how it can deal with the more complex questions of quantification and generalisation in diagrams that use more specific representations. This allows us to tackle difficult theorems that previously could only be proved algebraically.

Dr.Doodle: A Diagrammatic Theorem Prover

This paper presents the Dr.Doodle system, an interactive theorem prover that uses diagrammatic representations. The assumption underlying this project is that, for some domains (principally geometry), diagrammatic reasoning is easier to understand than conventional algebraic approaches – at least for a significant number of people. The Dr.Doodle system was developed for the domain of metric-space analysis (a geometric domain, but traditionally taught using a dry algebraic formalism). Pilot experiments were conducted to evaluate its potential as the basis of an educational tool, with encouraging results.

Aligning syntax and semantics in formalisations of visual languages

Often the most effective diagrams are those which are very simple. However there is a strong tendency, particularly prevalent in visual formal modelling and specification languages, to take a diagrammatic language which at core is very simple, and then add many extensions and features to make it more expressive - often making it so expressive that the diagrams produced in the language are no longer readable; or at least, the diagrams are no longer obviously a more effective form of representation than a text-based one. Both the design of effective visual formal modelling and specification languages, and the effective formalisation of (the semantics of) such visual languages requires the unification of results from visual language theory, cognitive science, empirical psychology and graphic design. Integrating results from such diverse fields is a non-trivial task, which may be approached through a decomposition of the study of issues of effectiveness in diagrammatic languages according to analogous understandings of (written and spoken) natural languages.

The Persuasion Machine

The aim of this chapter is to explore the problems and challenges of creating a ‘Persuasion Machine’ that is intended to engage a user in an argument in order to persuade her of some point of view. The approach is to start with a focus upon breadth, and to bring structure to an ill-structured problem. From there, for each component and each subproblem, the linguistic, computational, rhetorical and argumentation-theoretic theory drivers are integrated, to develop scaffolding and solutions that work not only as an environment in which to assess new theoretical developments, but also as a route to implementation and evaluation.

Formalising pragmatic features of graph-based notations

Graph-based notations form a significant subclass of visual languages. Studies of the use of such notations in practice have shown that users often employ pragmatic aspects, such as layout, to capture important domain information. Moreover this pragmatic information can support and guide reasoning over such representations. However, typical formalisations of graph-based notations often pay scant regard to such pragmatic considerations. This paper highlights an algebraic account of graph-based notations which is sensitive to relevant layout information. We illustrate, with examples taken from software engineering practice, how this algebra both captures pragmatic aspects of graphs and supports direct reasoning over their structure.

Human–formalism interaction: Studies in communication through formalism

Abstract A recurrent theme in studying the interaction between human and formalism is the understanding of how people interact with representations in reasoning and communication. In contrast to the best known theories, which approach the question of the impact of representation upon reasoning through explanations in terms of human computational architecture, we present here a more fundamental approach. This approach separates the problem into two parts—issues about computational complexity arising from the nature of the semantic interpretation (issues which are abstract with regard to architecture); and issues about how human computational architecture in particular can be brought to bear on different representations. On this view, for example, diagrams are often logically inexpressive and this is why they lead to efficient inference. This paper presents experiences in applying this semantic approach to the empirical study of modality assignment in three disparate domains: logic teaching, safety critical software engineering and the teaching of formality. We show how, in each of these cases, an account of the semantics of representations in simple formal terms permits the analysis and modelling of what would otherwise be incomprehensibly complicated behavioural phenomena. The results of these apparently diverse studies indicate that individual differences in what might be termed cognitive styles have a significant effect upon a humans use and understanding of various formalisms. This, we argue, is evidence that HCI researchers require a more analytical means to relate the cognitive and social sides of HCI than has previously been available. Furthermore, we also take the studies presented here as evidence that our approach is a substantial step towards providing such a means of analysis.

An Experimental Comparison of Diagrammatic and Algebraic Logics

We have developed a diagrammatic logic for theorem proving, focusing on the domain of metric-space analysis (a geometric domain, but traditionally taught using a dry algebraic formalism). To evaluate its pragmatic value, pilot experiments were conducted using this logic – implemented in an interactive theorem prover – to teach undergraduate students (and comparing performance against an equivalent algebraic logic). Our results show significantly better performance for students using diagrammatic reasoning. We conclude that diagrams are a useful tool for reasoning in such domains.

Knowledge engineering in the communication of Information for safety critical systems

The design and assessment of safety critical systems often involves broad and distributed teams of designers, suppliers and analysts who represent diverse areas of expertise and motivations. Accurate and effective communication between these groups is therefore an issue of primary importance. The formalisation of specifications and arguments of safety can be of significant benefit in ensuring the consistency of evidence in such cases, when it must be presented across many domains. However, a formal description of a safety critical system may be unconvincing unless it is presented in a form which is (or forms which are) accessible to the broad range of users and assessors of safety cases. This raises issues of human communication which include the tailoring of information to particular communicative tasks; the efficacy of differing media for communication and the cognitive impact that such differing media have. This paper draws together work in fields of knowledge engineering, knowledge based systems and human communication in an effort to address, from a sound theoretical basis, these and other communication issues raised by the use of formal descriptions in safety critical systems. Further, this paper argues that a primary role for knowledge based systems techniques in safety critical systems is in supporting the communication of information.