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Analysing interactive devices based on information resource constraints

Analysing interactive devices based on information resource constraints

Analysis of the usability of an interactive system requires both an understanding of how the system is to be used and a means of assessing the system against that understanding. Such analytic assessments are particularly important in safety-critical systems as latent vulnerabilities may exist which have negative consequences only in certain circumstances. Many existing approaches to assessment use tasks or scenarios to provide explicit representation of their understanding of use. These normative user behaviours have the advantage that they clarify assumptions about how the system will be used but have the disadvantage that they may exclude many plausible deviations from these norms. Assessments of how a design fails to support these user behaviours can be a matter of judgement based on individual experience rather than evidence. We present a systematic formal method for analysing interactive systems that is based on constraints rather than prescribed behaviour. These constraints capture precise assumptions about what information resources are used to perform action. These resources may either reside in the system itself or be external to the system. The approach is applied to two different medical device designs, comparing two infusion pumps currently in common use in hospitals. Comparison of the two devices is based on these resource assumptions to assess consistency of interaction within the design of each device.

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Reusing models and properties in the analysis of similar interactive devices

Reusing models and properties in the analysis of similar interactive devices

Variations between user interface designs are often relatively subtle and do not always become evident through even relatively thorough user testing. Notwithstanding their subtlety, these differences may be important to the safety or usability of a device. To address this, we are using model checking techniques for checking systematically a set of template properties that are designed to explore important interface characteristics. We have applied the approach to two devices designed to support similar tasks in a clinical setting (two infusion pumps). The analysis of the two infusion pumps provides solid evidence of areas of concern where redesign would reduce complexity and increase the reliability of the two designs.