Showing papers presented at "Conference on Computability in Europe in 2008"

Toward an understanding of flow in video games

Abstract: In the domain of computer games, research into the interaction between player and game has centred on 'enjoyment', often drawing in particular on optimal experience research and Csikszentmihalyi's 'Flow theory'. Flow is a well-established construct for examining experience in any setting and its application to game-play is intuitive. Nevertheless, it's not immediately obvious how to translate between the flow construct and an operative description of game-play. Previous research has attempted this translation through analogy. In this article we propose a practical, integrated approach for analysis of the mechanics and aesthetics of game-play, which helps develop deeper insights into the capacity for flow within games. The relationship between player and game, characterized by learning and enjoyment, is central to our analysis. We begin by framing that relationship within Cowley's user-system-experience (USE) model, and expand this into an information systems framework, which enables a practical mapping of flow onto game-play. We believe this approach enhances our understanding of a player's interaction with a game and provides useful insights for games' researchers seeking to devise mechanisms to adapt game-play to individual players.

People, places, and play: player experience in a socio-spatial context

Abstract: Digital games frequently give rise to engaging and meaningful social interactions, both over the internet and in the real and tangible world of the gamer. This is the focus of the present paper, which explores digital gaming as a situated experience, shaped by socio-spatial contingencies. In particular we discuss how co-players, audience, and their spatial organization shape play and player experience and review supporting evidence for this. We present a framework describing social processes underlying situated social play experience and how these are shaped by the player the game's socio-spatial and media context. The core of this framework describes various 'sociality characteristics', and discusses these both in terms of co-located and mediated social game settings.

NEAT-o-Games: blending physical activity and fun in the daily routine

Abstract: This article describes research that aims to encourage physical activity through a novel pervasive gaming paradigm. Data from a wearable accelerometer are logged wirelessly to a cell phone and control the animation of an avatar that represents the player in a virtual race game with other players over the cellular network. Winners are declared every day and players with an excess of activity points can spend some to get hints in mental games of the suite, like Sudoku. The racing game runs in the background throughout the day and every little move counts. As the gaming platform is embedded in the daily routine of players, it may act as a strong behavioral modifier and increase everyday physical activity other than volitional sporting exercise. Such physical activity (e.g., taking the stairs), is termed NEAT and was shown to play a major role in obesity prevention and intervention. A pilot experiment demonstrates that players are engaged in NEAT-o-Games and become more physically active while having a good dosage of fun.

Extraction in Coq: An Overview

Abstract: The extraction mechanism of Coq allows one to transform Coq proofs and functions into functional programs. We illustrate the behavior of this tool by reviewing several variants of Coq definitions for Euclidean division, as well as some more advanced examples. We then continue with a more general description of this tool: key features, main examples, strengths, limitations and perspectives.

Trends in the living room and beyond: results from ethnographic studies using creative and playful probing

Abstract: In this article we present the findings of two ethnographic studies embedded into two broader projects on interactive television in the home environment. Based on previous research on the home context and inspired by ongoing trends around interactive television, we explored basic concepts, such as the extended home, and new interaction techniques, in particular those related to future developments of the remote control. For the two studies we also developed two variations of the cultural probes method: creative probing and playful probing. This methodological approach proved to be appropriate for gathering in-depth data on participants' opinions, attitudes, and ideas in a way favorable to the participants. Overall, our results support existing research data on user media behavior and expectations and show trends in and beyond the living room, concerned with personalization, privacy, and security as well as communication.

Massively multiplayer online role-playing games: the past, present, and future

Abstract: Massively multiplayer online role-playing games (MMORPGs) are emerging in the computer game industry as a very popular genre. These games have existed since the late 1990s, but in the last few years the market has become increasingly strong. This relatively new genre is attracting a widespread audience, bringing together those who previously enjoyed both pen and paper and computer role-playing games, as well as those who enjoy socializing with other players in a virtual environment. Game developers see MMORPGs as a potentially profitable business due to its widespread appeal, but the reality is that only a small percentage of MMORPGs that are released become a success [Kosak 2006]. This article attempts to determine the many aspects that make a successful MMORPG; it also attempts to ascertain what new and innovative features are expected by the users from the next generation of MMORPGs. This is achieved by looking at and discussing past literature and surveying the MMORPG community's perception of previous and current MMORPGs, as well as their expectations of the next generation. An online survey attracted 122 participants to provide their perceptions of current and past MMORPGs. This article determines and outlines the respondents' preferences in the MMORPG genre, discussing what implications these could have on its future. The survey also gave insight into the respondents' expectations of the future of MMORPGs. We conclude this article with a discussion of aspects of current MMORPGs that the participants would like improved, as well as new features they would like incorporated into the next generation of games.

The role of semantics in games and simulations

Abstract: Powerful graphics hardware is enabling strong improvements in both the appearance and the complexity of virtual worlds for games and simulations. However, current practices in the design and development of virtual worlds mostly resemble high-tech variants of traditional handcrafts, resulting in increasingly unbearable design costs. In this article we state that an essential key to overcoming these problems lies in the enrichment of object models with several kinds of semantic data. We discuss numerous and promising uses for semantic information in virtual worlds, and show, for many of them, how previous results of recent research can be successfully applied. We also identify the fundamental challenges in this new cross-disciplinary area, and point out a number of open issues lying ahead, including the need for (i) a suitable way of specifying semantic data, providing a powerful vocabulary that is useful and usable for all disciplines involved in game design and development; (ii) a seamless integration of semantic data integrated with procedural generation techniques, in order to provide designers with a new and powerful generation of tools; and (iii) a consistency maintenance among evolving objects in a changeable environment, for which powerful constraint-solving methods will be instrumental. We conclude that, as the expectancy for future games and simulations steadily shifts from improved graphics and appearance towards improved character behavior, plausible realism and coherent gameplay, embedding the game world and its objects with richer semantics is going to play a crucial role. We can therefore expect that, in the near future, increasing research efforts and influential results will be emerging in this new exciting area.

The uses of social television

Abstract: We present the results of two studies on social television concepts. In one study, a social TV prototype was tested in the field, allowing groups of users watching television at home to talk to each other over an audio link. Specific patterns of use are described, showing that users did perceive the system as valuable. In another study, focus groups were presented with several social TV concepts, and their responses were collected. These participants saw only moderate to marginal value in the concept. We discuss the discrepancy with reference to the limitations of each method. Based on our analysis, we conclude that our social television experience provides user value under certain favorable conditions. Participants deal with potential conflicts between conversation and television audio without the need for additional technical support, and there is no indication that a video link would improve the experience. However, designing for the social dynamics at the beginnings, ends, and outside of conversations remains an open challenge.

Social television and user interaction

Abstract: At first glance, the notion of social interactive television seems to be a tautology. Television watching has always been a social activity. People watch television together in their living rooms, and outside their homes they talk about last night's football match; and even call each other to recommend an interesting program. Unfortunately, until recently, research on social interactive television has been scarce. One limiting factor for the development of innovative services for the home is the interactive technology behind user interaction, which was limited to the remote control. Fortunately, a number of studies concentrate on extending interactive methods, for example by using contextual information. This article reviews the state of the art in these two directions: the social aspects of television and user interaction. We conclude with a research agenda for further research, which might transform current interactive television services into shared experiences.

Temporal interaction between an artificial orchestra conductor and human musicians

Abstract: The Virtual Conductor project concerns the development of the first properly interactive virtual orchestra conductor—a Virtual Human that can conduct a piece of music through interaction with musicians, leading and following them while they are playing. This article describes our motivation for developing such a system; related work in the areas of ambient entertainment and coordinated timing, automatic music processing, virtual humans, and conducting; the design, implementation, and evaluation of the Virtual Conductor, and, finally, contains a discussion of the resulting system and expected developments in the (still ongoing) Virtual Conductor project.

Designing new interfaces for digital interactive television usable by older adults

Abstract: The adoption of digital television (DTV), if appropriately designed, could be particularly attractive for older people, who tend to be overlooked when new services and applications are introduced, and remain a marginalized segment of the television broadcasting population. This article explores a range of methodologies and interactive approaches designed to support older people who have difficulties in using current interface models for DTV. Following an extensive requirements-gathering exercise, four different navigational layouts with a simplified remote control were tested and evaluated with older users to assess their ease of use. The results demonstrated the expected difficulties in understanding some of the terminology and interactive concepts utilized in "traditional" DTV design. Aspects of the experimental layouts suggest promising new directions in the development of visualization and navigation metaphors for user-led activities on DTV for older adults.

Succinct NP Proofs from an Extractability Assumption

Abstract: We prove, using a non-standard complexity assumption, that any language in has a 1-round(that is, the verifier sends a message to the prover, and the prover sends a message to the verifier) argument system (that is, a proof system where soundness holds against polynomial-time provers) with communication complexity only polylogarithmic in the size of the instance. We also show formal evidence that the nature of the non-standard complexity assumption we use is analogous to previous assumptions proposed in the cryptographic literature. The question of whether complexity assumptions of this nature can be considered acceptable or not remains of independent interest in complexity-theoretic cryptography as well as complexity theory.

Interpreting Localized Computational Effects Using Operators of Higher Type

Abstract: We outline a general approach to providing intensional models for languages with computational effects, whereby the problem of interpreting a given effect reduces to that of finding an operator of higher type satisfying certain equations. Our treatment consolidates and generalizes an idea that is already implicit in the literature on game semantics. As an example, we work out our approach in detail for the case of fresh name generation, and discuss some particular models to which it applies.

Embedded noninteractive continuous bot detection

Abstract: Multiplayer online computer games are quickly growing in popularity, with millions of players logging in every day. While most play in accordance with the rules set up by the game designers, some choose to utilize artificially intelligent assistant programs, a.k.a. bots, to gain an unfair advantage over other players. In this article we demonstrate how an embedded noninteractive test can be used to prevent automatic artificially intelligent players from illegally participating in online game-play. Our solution has numerous advantages over traditional tests, such as its nonobtrusive nature, continuous verification, and simple noninteractive and outsourcing-proof design.

Using “tilt” as an interface to control “no-button” 3-D mobile games

Abstract: Mobile phones offer considerable challenges for game developers, and not least among them is the user interface, which is primarily optimized for number entry rather than for playing games. In fact, due to the limitations one of the most desirable criteria for mobile games has the design of games controlled by a one-button interface. However, this type of interface has only been seen as applicable for casual games, where mastering the interface is de-emphasized. As a number of mobile phones are starting to appear with 3-D accelerometers, game developers have the opportunity to investigate new interface mechanisms. In this article we illustrate how accelerometers provide the possibility of a no-button mobile game. While 3-D accelerometers offer a range of possible interface mechanisms, the one that requires minimal signal processing and no external references is motion, and in particular, tilt, and as such is eminently suitable for mobile phones. In this article we explore a tilt interface for a 3-D graphics first-person driving game titled Tunnel Run, and compare the user experience playing the same game with a traditional phone joypad interface and with a tilt interface in two different modes. The results show that the tilt interface was experienced as fun, and certainly seemed more attractive to players, who said they would not have played this type of game otherwise.

Reachability in Linear Dynamical Systems

Abstract: Dynamical systems allow to modelize various phenomena or processes by only describing their local behaviour It is however useful to understand the behaviour in a more global way Checking the reachability of a point for example is a fundamental problem In this document we will show that this problem that is undecidable in the general case is in fact decidable for a natural class of continuous-time dynamical systems: linear systems For this, we will use results from the algebraic numbers theory such as Gelfond-Schneider's theorem

Two-by-Two Substitution Systems and the Undecidability of the Domino Problem

Abstract: Thanks to a careful study of elementary properties of two-by-two substitution systems, we give a complete self-contained elementary construction of an aperiodic tile set and sketch how to use this tile set to elementary prove the undecidability of the classical Domino Problem

Computability and Complexity in Self-assembly

Abstract: This paper explores the impact of geometry on computability and complexity in Winfree's model of nanoscale self-assembly. We work in the two-dimensional tile assembly model, i.e., in the discrete Euclidean plane ? ×?. Our first main theorem says that there is a roughly quadratic function fsuch that a set A? ?+is computably enumerable if and only if the set X A = { (f(n), 0) | n? A} --- a simple representation of Aas a set of points on the x-axis --- self-assembles in Winfree's sense. In contrast, our second main theorem says that there are decidable sets D? ? ×? that do notself-assemble in Winfree's sense. Our first main theorem is established by an explicit translation of an arbitrary Turing machine Mto a modular tile assembly system $\mathcal{T}_M$, together with a proof that $\mathcal{T}_M$ carries out concurrent simulations of Mon all positive integer inputs.

An Enhanced Theory of Infinite Time Register Machines

Abstract: Infinite time register machines(ITRMs) are register machines which act on natural numbers and which are allowed to run for arbitrarily many ordinal steps Successor steps are determined by standard register machine commands At limit times a register content is defined as a $\liminf$ of previous register contents, if that limit is finite; otherwise the register is resetto 0 (A previous weaker version of infinitary register machines, in [6], would halt without a result in case of such an overflow) The theory of infinite time register machines has similarities to the infinite time Turing machines (ITTMs) of Hamkins and Lewis Indeed ITRMs can decide all $\Pi^1_1$ sets, yet they are strictly weaker than ITTMs

A goal-oriented development tool to automate the incorporation of intelligent agents into interactive digital media applications

Abstract: Recent developments in games and interactive storytelling applications have seen artificially intelligent computer controlled characters being included extensively. Non-human controlled characters are starting to play an increasingly significant role in enhancing the perceived intelligence of games. Although many of them employed certain cheating techniques (e.g. allocating more resources at the start to AI opponents to make them appear more aggressive), some limited learning did appear in several games (e.g. letting AI opponents remember where human users initiated attacked in previous game). In our Virtual Singapura research project, we incorporate software agents into our virtual world to provide more complex user interactions. With intelligent software agents being infused into interactive digital media applications, there is great potential in improving the overall user experience. However, during the process of our research, we discovered that the traditional way of adding a multi-agent system into a computer game requires a large amount of investment in time and resources and a high level of expertise in Agent Oriented Software Engineering (AOSE). Moreover, game AI is usually closely coupled with other parts of the game code which makes it hard to reuse or replace. This research proposes a multi-agent development and runtime framework which not only provides ease-of-use agent design and implementation tools but also can be easily plugged into various interactive digital media applications.

Linear, Polynomial or Exponential? Complexity Inference in Polynomial Time

Abstract: We present a new method for inferring complexity properties for imperative programs with bounded loops. The properties handled are: polynomial (or linear) boundedness of computed values, as a function of the input; and similarly for the running time. It is well known that complexity properties are undecidable for a Turing-complete programming language. Much work in program analysis overcomes this obstacle by relaxing the correctness notion: one does not ask for an algorithm that correctly decides whether the property of interest holds or not, but only for "yes" answers to be sound. In contrast, we reshaped the problem by defining a "core" programming language that is Turing-incomplete, but strong enough to model real programs of interest. For this language, our method is the first to give a certain answer; in other words, our inference is both sound and complete. The essence of the method is that every command is assigned a "complexity certificate", which is a concise specification of dependencies of output values on input. These certificates are produced by inference rules that are compositional and efficiently computable. The approach is inspired by previous work by Niggl and Wunderlich and by Jones and Kristiansen, but use a novel, more expressive kind of certificates.

Using prototypes in early pervasive game development

Abstract: In this article we discuss various prototyping methods in early pervasive game development. The focus is on pervasive games that are played with mobile phones. Choosing the right prototyping method is crucial in achieving results that can be used for validating or developing further design ideas. In this article we give guidelines that help the selection process and give ideas on methods that can be used in different situations. We have play-tested pervasive game prototypes using agile software prototype development methods, forum prototypes, and guided paper prototyping methods. We give examples of five pervasive games where these kinds of prototyping methods are used. In concluding, we compare the results and discuss their benefits and disadvantages in the game development process, that is, when the methods should be used and what should be considered when using them.

Mobio threat: A mobile game based on the integration of wireless technologies

Abstract: Pervasive gaming is a new genre that became possible due to the development of communication technologies, especially wireless ones In this area of gaming, players must physically walk to certain places of the game area to reach their objectives and missions They may also interact with the environment and with real objects Nowadays, there are just a few pervasive games developed, and all of them have limitations concerning localization tracking, hardware flexibility, signal coverage, and cheap setup In this context, an innovative game, called moBIO Threat // Disease Control, was developed on the basis of the integration of multiple wireless technologies, mixing their capabilities and neutralizing their limitations It utilizes RFID, IrDA, and QR Code technologies for object interaction, Bluetooth for exchanging information between players who are physically close and the IEEE 80211 Wi-Fi protocol to connect all of the players with the game server From what we observed, moBIO Threat provides a completely different game experience, with social gaming and collaboration being strong attributes of the game This article describes the development of the game and other details about the project and about pervasive gaming

The Relative Consistency of the Axiom of Choice -- Mechanized Using Isabelle/ZF

Abstract: Godel [3] published a monograph in 1940 proving a highly significant theorem, namely that the axiom of choice (AC) and the generalized continuum hypothesis (GCH) are consistent with respect to the other axioms of set theory. This theorem addresses the first of Hilbert's famous list of unsolved problems in mathematics. I have mechanized this work [8] using Isabelle/ZF [5,6]. Obviously, the theorem's significance makes it a tempting challenge; the proof also has numerous interesting features. It is not a single formal assertion, as most theorems are. Godel [3, p. 33] states it as follows, using Σto denote the axioms for set theory: What we shall prove is that, if a contradiction from the axiom of choice and the generalized continuum hypothesis were derived in Σ, it could be transformed into a contradiction obtained from the axioms of Σalone. Godel presents no other statement of this theorem. Neither does he introduce a theory of syntax suitable for reasoning about transformations on proofs, surely because he considers it to be unnecessary

The evaluation of ARCO: a lesson in curatorial competence and intuition with new technology

Abstract: This article presents the results of the evaluation study of the Augmented Representation of Cultural Objects (ARCO) system which provides software and interface tools to museum curators for the development of virtual museum exhibitions for the World Wide Web or for information kiosks. The aim of the current research is to investigate how a virtual museum system is coping with the demands of museum curators, to examine the needs of virtual museum visitors, and to provide a set of criteria and guidelines for defining effective evaluation of such systems. Evaluation methods such as heuristic evaluation and walkthroughs were employed in the study in order to assess various components and interfaces of the system.

How We Think of Computing Today

Abstract: Classical models of computation no longer fully correspond to the current notions of computing in modern systems. Even in the sciences, many natural systems are now viewed as systems that compute. Can one devise models of computation that capture the notion of computing as seen today and that could play the same role as Turing machines did for the classical case? We propose two models inspired from key mechanisms of current systems in both artificial and natural environments: evolving automata and interactive Turing machines with advice. The two models represent relevant adjustments in our apprehension of computing: the shift to potentially non-terminating interactive computations, the shift towards systems whose hardware and/or software can change over time, and the shift to computing systems that evolve in an unpredictable, non-uniform way. The two models are shown to be equivalent and both are provably computationally more powerful than the models covered by the old computing paradigm. The models also motivate the extension of classical complexity theory by non-uniform classes, using the computational resources that are natural to these models. Of course, the additional computational power of the models cannot in general be meaningfully exploited in concrete goal-oriented computations.

A Simple P-Matrix Linear Complementarity Problem for Discounted Games

Abstract: The values of a two-player zero-sum binary discounted game are characterized by a P-matrix linear complementarity problem (LCP). Simple formulas are given to describe the data of the LCP in terms of the game graph, discount factor, and rewards. Hence it is shown that the unique sink orientation (USO) associated with this LCP coincides with the strategy valuation USO associated with the discounted game. As an application of this fact, it is shown that Murty's least-index method for P-matrix LCPs corresponds to both known and new variants of strategy improvement algorithms for discounted games.

Hybrid Functional Interpretations

Abstract: We show how different functional interpretations can be combined via a multi-modal linear logic. A concrete hybrid of Kreisel's modified realizability and Godel's Dialectica is presented, and several small applications are given. We also discuss how the hybrid interpretation relates to variants of Dialectica and modified realizability with non-computational quantifiers.

Modeling motivation for adaptive nonplayer characters in dynamic computer game worlds

Abstract: Current computer games are being set in increasingly more complex and dynamic virtual environments. Massively multiplayer online games, for example, are played in persistent virtual worlds, which evolve and change as players create and personalize their own virtual property. In contrast, technologies for controlling the behavior of nonplayer characters that populate virtual game worlds are frequently limited to preprogrammed rules. Characters using fixed rule-sets lack the ability to adapt in time with their environment. Motivated reinforcement learning offers an alternative to character design that can achieve nonplayer characters that both evolve and adapt in dynamic environments. This article presents and evaluates two computational models of motivation for use in nonplayer characters in persistent computer game worlds. These models represent motivation as an ongoing search for novelty, interest, and competence. Two metrics are introduced to evaluate the adaptability of characters controlled by motivated reinforcement learning agents using different models of motivation. These metrics characterize the behavior of nonplayer characters in terms of the variety and complexity of learned behaviors. An empirical evaluation of characters in simulated game scenarios shows that characters motivated by the search for competence are more adaptable in dynamic environments than those motivated by interest and novelty alone.

Providing expressive gaze to virtual animated characters in interactive applications

Abstract: Eyes play an important role in communication among people. Motions of the eye express emotions and regulate the flow of conversation. Hence we consider fundamental that virtual humans or other characters present convincing and expressive gaze in applications such as Embodied Conversational Agents (ECAs), games and movies. However, we perceive that in many applications that require automatic generation of facial movements, such as ECA, character's eye motion does not carry meaning related to its expressiveness. This work proposes a model for the automatic generation of expressive gaze by examining eye behavior in different affective states. To collect data related to gaze and expressiveness, we looked at Computer Graphics movies. This data was used as a basis to describe gaze expressions in the proposed model. We also implemented a prototype and performed some tests with users in order to observe the impact of eye behavior during some expressions of emotion. The results show that the model is capable of generating eye motions that are coherent with the affective states of the virtual character.