This paper combines the vocabulary of semiotics and category theory to provide a formal analysis of visualization. It shows how familiar processes of visualization fit the semiotic frameworks of both Saussure and Peirce, and extends these structures using the tools of category theory to provide a general framework for understanding visualization in practice, including: Relationships between systems, data collected from those systems, renderings of those data in the form of representations, the reading of those representations to create visualizations, and the use of those visualizations to create knowledge and understanding of the system under inspection. The resulting framework is validated by demonstrating how familiar information visualization concepts (such as literalness, sensitivity, redundancy, ambiguity, generalizability, and chart junk) arise naturally from it and can be defined formally and precisely. This paper generalizes previous work on the formal characterization of visualization by, inter alia, Ziemkiewicz and Kosara and allows us to formally distinguish properties of the visualization process that previous work does not.

A novel concept for improving the trustworthiness of results obtained from digital investigations is presented. Case Based Reasoning Forensic Auditor (CBR-FA) is a method by which results from previous digital forensic examinations are stored and reused to audit current digital forensic investigations. CBR-FA provides a method for evaluating digital forensic investigations in order to provide a practitioner with a level of reassurance that evidence that is relevant to their case has not been missed. The structure of CBR-FA is discussed as are the methodologies it incorporates as part of its auditing functionality.

In this paper, we reflect upon the investigations into external auditory representations of programs (program auralization) reported by Vickers and Alty at ICAD 2000. First, we place the work in its historical and thematic context and explore the motivation that lay behind it. We then outline the process by which we got to the stage of being able to report empirical results in 2000 and compare the work with that done by other researchers in the field. Finally, we assess the major contribution that this work made to the field of auditory display and look to the future outlining the work still to be done since the paper was first published (we also look at work done by others in this area since 2000).

Program auralization aims to communicate information about program state, data, and behavior using audio. We have argued that music offers many advantages as a communication medium [Alty 1995]. The CAITLIN system [Alty and Vickers 1997; Vickers 1999; Vickers and Alty 1996, 1998] was constructed to provide auralizations within a formal structured musical framework. Pilot studies [Alty and Vickers 1997; Vickers 1999] showed that programmers could infer program structure from auralizations alone. A study was conducted using 22 novice programmers to assess (i) whether novices could understand the musical auralizations and (ii) whether the musical experience and knowledge of subjects affected their performance. The results show that novices could interpret the auralizations (with accuracy varying across different levels of abstraction) and that musical knowledge had no significant effect on performance. A second experiment was conducted with another 22 novice programmers to study the effects of musical program auralization on debugging tasks. The experiment aimed to determine whether auralizations would lead to higher bug detection rates. The results indicate that, in certain circumstances, musical auralizations can be used to help locate bugs in programs and that musical skill does not affect the ability to make use of the auralizations. In addition, the experiment showed that subjective workload increased when the musical auralizations were used.

The audio channel remains little used in most computing applications, often its use being relegated to providing trivial sound effects whose novelty value soon wears off. Nevertheless, in principle sound offers much to the process of human–computer interaction as for most people the notion of auditory imagery is easily accepted. In this paper we explore how sound, specifically musical sound, can be used to communicate computing information. The findings of two studies are presented. The first investigated how pitch intervals and musical phrases of complex (non-sinusoidal) tones can be recognised. The second study aimed to demonstrate that musical structures could communicate information about high-level programming language structures and program run-time behaviour. Both studies showed that music could successfully be used as a communication medium and that listeners did not need to be musically trained to benefit from the audio signals. Finally, recommendations for further work are made.

In an earlier paper, Vickers and Alty (2002) showed that musically untrained users could make use of musical cues to understand computing information. Using a technique known as musical program auralisation, they showed that music could communicate run-time and structural information about Pascal programs. This paper describes how a set of hierarchically related auralisation motifs was designed and constructed within a formal musical framework. These auralisations were then evaluated in an experiment to determine how well they could be interpreted by computer science students. The results showed that the musical motifs were generally understood by the subjects and that any prior musical training of the subjects did not affect their ability to interpret the musical signals. Based on the results of the experiment and study of some cognitive aspects of music perception, a set of organising principles for musical program auralisation is proposed. Finally, recommendations for further study are made with particular regard to assessing the usefulness of the auralisations in program debugging situations.

In The Songs of Insects, Pierce (1949) described the striped ground cricket, Nemobius fasciatus-fasciatus, which chirps at a rate proportional to ambient air temperature. Twenty chirps-per-second tell us it is 31.4 °C; 16 chirps and it is 27 °C. This is a natural example of an auditory display, a mechanism for communicating data with sound. By applying auditory display techniques to computer programming we have attempted to give the bugs that live in software programs their own songs. We have developed the CAITLIN musical program auralisation system Vickers and Alty, 2002b) to allow structured musical mappings to be made of the constructs in Pascal programs. Initial experimental evaluation [Interacting with Computers (2002a,b)] showed that subjects could interpret the musical motifs used to represent the various Pascal language constructs. In this paper we describe how the CAITLIN system was used to study the effects of musical program auralisation on debugging tasks performed by novice Pascal programmers. The results of the experiment indicate that a formal musical framework can act as a medium for communicating information about program behaviour, and that the information communicated could be used to assist with the task of locating bugs in faulty programs.