Telescreens, keypens, and the expert: A 60 year snapshot

Brian Shackel was responsible for initiating the first international conference on human–computer interaction, INTERACT ’84. This was in the same year to which George Orwell referred in the now-classic book, Nineteen Eighty-Four. Both texts share the common theme of being concerned with information and its effects on the individual. In Professor Shackel’s paper (the focus here), both aspects are considered over a 60-year lifespan – with a particular emphasis on his interest on “Designing for People in the Age of Information”. This keynote address at the INTERACT conference is reviewed and the accuracy of his many predictions for the future considered. It is concluded that despite Professor Shackel’s preoccupation with designing for humans some quarter of a century ago, there still is much work to do.     

Spatial strategies in a generalized spatial prisoner’s dilemma

Many strategies, such as tit-for-tat, have been proposed in the iterated prisoner’s dilemma (IPD) in which the prisoner’s dilemma (PD) is carried out repeatedly with two players. A spatial version of the iterated prisoner’s dilemma (SPD) has been studied, where a player at each site plays the IPD game with all the players in the neighborhood. However, the strategies studied in the SPD consider the past actions of a single opponent only. We studied spatial strategies that depend on the configuration of actions taken by all neighbors (as opposed to conventional temporal strategies). Since generosity can be considered as a spatial strategy, we first investigate the generosity required when an action error is involved. We also propose several spatial strategies that outperform many others.This work was presented, in part, at the 9th International Symposium on Artificial Life and Robotics, Oita, Japan, January 28–30, 2004     

Revisiting the notion of function

Functions play a central role in type theory, logic and computation. We describe how the notions of functionalisation (the way in which functions can be constructed) and instantiation (the process of applying a function to an argument) have been developed in the last century. We explain how both processes were implemented in Frege’s Begriffschrift, Russell’s Ramified Type Theory, and the λ-calculus (originally introduced by Church) showing that the λ-calculus misses a crucial aspect of functionalisation. We then pay attention to some special forms of function abstraction that do not exist in the λ-calculus and we show that various logical constructs (e.g., let expressions and definitions and the use of parameters in mathematics), can be seen as forms of the missing part of functionalisation. Our study of the function concept leads to: (a) an extension of the Barendregt cube [4] with all of definitions, Π-reduction and explicit substitutions giving all their advantages in one system; and (b) a natural refinement of the cube with parameters. We show that in the refined Barendregt cube, systems like A , LF, and ML, can be described more naturally and accurately than in the original cube.     

A sensitivity formula for risk-sensitive cost and the actor–critic algorithm

We propose for risk sensitive control of finite Markov chains a counterpart of the popular ‘actor–critic’ algorithm for classical Markov decision processes. The algorithm is based on a ‘sensitivity formula’ for the risk sensitive cost and is shown to converge with probability one to the desired solution. The proof technique is an adaptation of the ordinary differential equations approach for the analysis of two time-scale stochastic approximation algorithms.     

A generalization of ACP using Belnap’s logic

ACP is combined with Belnap’s four-valued logic via conditional composition (if–then–else). We show that the operators of ACP can be seen as instances of more general, conditional operators. For example, both the choice operator + and δ (deadlock) can be seen as instances of conditional composition, and the axiom x + δ = x follows from this perspective. Parallel composition is generalized to the binary conditional merge _ψ where covers the choice between interleaving and synchronization, and ψ determines the order of execution. The instance _BB is ACP’s parallel composition, where B (both) is the truth value that models both true and false in Belnap’s logic. Other instances of this conditional merge are sequential composition, pure interleaving and synchronous merge. We investigate the expression of scheduling strategies in the conditions of the conditional merge.     

A Comparative analysis of Green’s functions of 1D matching equations for motion synthesis

When filtering an input image, the Green’s functions of matching equations are capable of inducing a broad class of motions, a property that has led to their use in several computer graphics and computer vision applications. In all such applications, the Green’s functions of second-order differential equations have been considered, even though no justification has been given for their preference over simpler, first-order equations. Here we present a study of first-order one-dimensional matching equations, both in the uniform and in the affine motion models. Comparing their Green’s functions with those of the corresponding second-order cases, we find evidence for the latter’s superiority in motion synthesis. We also propose and discuss a general discretization scheme for Green’s functions of one-dimensional matching equations, showing that the affine motion model is particularly sensitive to the sampling frequency. In this case, we advocate the use of area sampling, for allowing realistic motion simulations.     

Modeling Multimodal Expression of User’s Affective Subjective Experience

With the growing importance of information technology in our everyday life, new types of applications are appearing that require the understanding of information in a broad sense. Information that includes affective and subjective content plays a major role not only in an individual’s cognitive processes but also in an individual’s interaction with others. We identify three key points to be considered when developing systems that capture affective information: embodiment (experiencing physical reality), dynamics (mapping experience and emotional state with its label) and adaptive interaction (conveying emotive response, responding to a recognized emotional state). We present two computational systems that implement those principles: MOUE (Model Of User Emotions) is an emotion recognition system that recognizes the user’s emotion from his/her facial expressions, and from it, adaptively builds semantic definitions of emotion concepts using the user’s feedback; MIKE (Multimedia Interactive Environment for Kansei communication) is an interactive adaptive system that, along with the user, co-evolves a language for communicating over subjective impressions.     

A Proof Search Specification of the π-Calculus

We present a meta-logic that contains a new quantifier (for encoding “generic judgments”) and inference rules for reasoning within fixed points of a given specification. We then specify the operational semantics and bisimulation relations for the finite π-calculus within this meta-logic. Since we restrict to the finite case, the ability of the meta-logic to reason within fixed points becomes a powerful and complete tool since simple proof search can compute this one fixed point. The quantifier helps with the delicate issues surrounding the scope of variables within π-calculus expressions and their executions (proofs). We shall illustrate several merits of the logical specifications we write: they are natural and declarative; they contain no side conditions concerning names of variables while maintaining a completely formal treatment of such variables; differences between late and open bisimulation relations are easy to see declaratively; and proof search involving the application of inference rules, unification, and backtracking can provide complete proof systems for both one-step transitions and for bisimulation.     

Identifying Volatility Clusters Using the PPM: A Sensitivity Analysis

Several previous works show that, in general, financial time series are characterized by periods of large volatility followed by periods of relative quitness. In this paper we consider the product partition model (PPM) to identify changes in the volatility extending it to identify multiple change points in normal variances assuming known means. Yao’s prior cohesions and a conjugate prior distribution for the variance – which in this case is a Inverted-Gamma distribution – are assumed. The ultimate goal is to provide a sensitivity analysis to the product estimates assuming different prior specifications for the parameter which indexes the Yao’s cohesions and also for the variance. We analyze a Chilean stock market return series and conclude that the product estimates for the volatility of this series are strongly influenced by the prior specifications of both parameters.     

H∞-norm and invariant manifolds of systems with state delays

The problem of finding bounds on the H_∞-norm of systems with a finite number of point delays and distributed delay is considered. Sufficient conditions for the system to possess an H_∞-norm which is less or equal to a prescribed bound are obtained in terms of Riccati partial differential equations (RPDE’s). We show that the existence of a solution to the RPDE’s is equivalent to the existence of a stable manifold of the associated Hamiltonian system. For small delays the existence of the stable manifold is equivalent to the existence of a stable manifold of the ordinary differential equations that govern the flow on the slow manifold of the Hamiltonian system. This leads to an algebraic, finite-dimensional, criterion for systems with small delays.