Formal Verification in the Design of Gestural Interaction

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A coordination model for interactive components

Although presented with a variety of ‘flavours’, the notion of an interactor, as an abstract characterisation of an interactive com- ponent, is well-known in the area of formal modelling techniques for interactive systems. This paper replaces traditional, hierarchical, ‘tree-like’ composition of interactors in the specification of complex interactive sys- tems, by their exogenous coordination through general-purpose software connectors which assure the flow of data and the meet of synchronisation constraints. The paper’s technical contribution is twofold. First a modal logic is defined to express behavioural properties of both interactors and connectors. The logic is new in the sense that its modalities are indexed by fragments of sets of actions to cater for action co-occurrence. Then, this logic is used in the specification of both interactors and coordination layers which orchestrate their interconnection

Automatic Verification of a Lip-Synchronisation Algorithm Using UPPAAL - Extended Version

We present the formal specification and verification of a lip synchronisation algorithm using the real-time model checker UPPAAL. A number of specifications of this algorithm can be found in the literature, but this is the first automatic verification. We take a published specification of the algorithm, code it up in the UPPAAL timed automata notation and then verify whether the algorithm satisfies the key properties of jitter and skew. The verification reveals some flaws in the algorithm. In particular, it shows that for certain sound and video streams the algorithm can timelock before reaching a prescribed error state

Synchronisation and Delay in a Formal Model of User Cognition

This work is part of a syndetic approach to the evaluation of the usability of interaction devices that takes into account the cognitive resources needed to use a device to perform particular tasks. In the syndetic approach both a cognitive model and a model of system behaviour are specified and brought together within a single framework in order to investigate their relations. The ICS model is such a cognitive model of human information processing. In this model the human information processing is depicted as a number of independent cognitive processes that cooperate by means of exchanging mental representations of the observed environment. The style in which the model is described is close to a data flow style, which is also one of the formal approaches used within Computer Science for the specification of systems behaviour. In this paper we present a data flow oriented representation of a simplified version of the ICS model in which we study the synchronisation and delay of the stre..

Refinement for Direct Manipulation Interfaces

This note discusses the extent to which state-based traditional refinement and behaviour oriented architectural design techniques are appropriate for reasoning about implementations using direct manipulation. We argue that at best traditional refinement can be used to provide a posit-and-prove existence proof, namely that it can be used to argue that a particular sequence of user manipulations can be regarded as satisfying the specified behaviour of an abstract operation, but that other important behaviour is not guaranteed. Architectural design enforces safety properties but it requires that the formal description of an object starts only after the object has been completely informally defined at the actual level of abstraction. As an example, we develop a VDM and a LOTOS specification of a simple game, Min, and demonstrate how the notations, the underlying theories, and the development methodologies and environments can be used to show that it is possible to implement (a move of) th..

Using Hybrid Automata to Support Human Factors Analysis of a Critical System

A characteristic that many emerging technologies and interaction techniques have in common is a shift towards tighter coupling between human and computer. In addition to traditional discrete interaction, more continuous interaction techniques, such as gesture recognition, haptic feedback and animation, play an increasingly important role. Additionally, many supervisory control systems (such as flight deck systems) already have a strong continuous element. The complexity of these systems and the need for rigorous analysis of the human factors involved in their operation leads us to examine formal and possibly automated support for their analysis. The fact that these systems have important temporal aspects and potentially involve continuous variables, besides discrete events, motivates the application of hybrid systems modelling, which has the expressive power to encompass these issues. Essentially, we are concerned with human-factors related questions whose answers are dependent on interactions between the user and a complex, dynamic system