Showing papers presented at "Conference on Computability in Europe in 2017"

An Introduction to Musical Metacreation

Abstract: Musical metacreation (MuMe), also known as musical computational creativity, is a subfield of computational creativity that focuses on endowing machines with the ability to achieve creative musical tasks, such as composition, interpretation, improvisation, accompaniment, mixing, etc. It covers all dimensions of the theory and practice of computational generative music systems, ranging from purely artistic approaches to purely scientific ones, inclusive of discourses relevant to this topic from the humanities. MuMe systems range from purely generative ones to a variety of interactive systems, such as those for computer-assisted composition and computer-assisted sound design. In order to better appreciate the many dimensions of this interdisciplinary domain and see how it overlaps and differs from research in computer music, this introduction provides a general entry point. After defining and introducing the domain, its context, and some of its terminology, we reflect on some challenges and opportunities for the field as a whole.

Serious Games for Early Identification of Developmental Dyslexia

Abstract: Developmental Dyslexia (DD) is a neurodevelopmental disorder affecting reading acquisition. DD cannot be diagnosed before starting the primary school; thereby, one of the main challenges is to obtain an early DD identification even during preschool years. Achieving this goal could help children at risk for DD to limit the impact of this disorder. To this aim, we have created a digital system composed of various serious games designed for predicting the risk of DD in preschoolers and potentially training specific skills impaired in this learning disability. Our set of serious games are designed to be accessible from any device, a computer with mouse and keyboard, but also a tablet with touch interface for younger children.

Automated Bug Finding in Video Games: A Case Study for Runtime Monitoring

Abstract: Runtime verification is the process of observing a sequence of events generated by a running system and comparing it to some formal specification for potential violations. We show how the use of a runtime monitor can greatly speed up the testing phase of a video game under development by automating the detection of bugs when the game is being played. We take advantage of the fact that a video game, contrarily to generic software, follows a special structure that contains a “game loop.” This game loop can be used to centralize the instrumentation and generate events based on the game's internal state. We report on experiments made on a sample of six real-world video games of various genres and sizes by successfully instrumenting and efficiently monitoring various temporal properties over their execution, including actual bugs reported in the games' bug tracking database in the course of their development.

GameFlow in Different Game Genres and Platforms

Abstract: The GameFlow model strives to be a general model of player enjoyment, applicable to all game genres and platforms. Derived from a general set of heuristics for creating enjoyable player experiences, the GameFlow model has been widely used in evaluating many types of games, as well as non-game applications. Initial applications of the GameFlow model were limited to real-time strategy games. However, in order to be considered a general model of player enjoyment in games, the GameFlow model needs to be applied to a more varied set of play experiences. In this article, we revisit the design of the GameFlow model, review the various applications and derivative models, and discuss on-going analysis of the model. Subsequently, we describe a study that aims to extend the initial validation of the GameFlow model to incorporate additional game types. We report the results of expert reviews conducted using the GameFlow criteria to evaluate first person shooter games on Sony PlayStation 3 and adventure games on Apple iPhone. Our findings provide insight into the manifestation of the GameFlow elements in these types of games and also highlight some of the genre-specific considerations in the application of the GameFlow model. Key issues are raised and discussed in relation to immersion, social interaction, and multiplayer games.

ImproteK: Introducing Scenarios into Human-Computer Music Improvisation

Abstract: This article focuses on the introduction of control, authoring, and composition in human-computer music improvisation through the description of a guided music generation model and a reactive architecture, both implemented in the software ImproteK. This interactive music system is used with expert improvisers in work sessions and performances of idiomatic and pulsed music and more broadly in situations of structured or composed improvisation. The article deals with the integration of temporal specifications in the music generation process by means of a fixed or dynamic “scenario” and addresses the issue of the dialectic between reactivity and planning in interactive music improvisation. It covers the different levels involved in machine improvisation: the integration of anticipation relative to a predefined structure in a guided generation process at a symbolic level, an architecture combining this anticipation with reactivity using mixed static/dynamic scheduling techniques, and an audio rendering module performing live re-injection of captured material in synchrony with a non-metronomic beat. Finally, it sketches a framework to compose improvisation sessions at the scenario level, extending the initial musical scope of the system. All of these points are illustrated by videos of performances or work sessions with musicians.

User-Generated Content in Pervasive Games

Abstract: User-generated content (UGC) is already incorporated in several computer game instances wherein the players may create, edit and release their own content to the game world, thus influencing the game's evolution as well as the experience of other players. Lately, pervasive games have emerged as an exciting new development in gaming extending the boundaries of play out in the real word. The effectiveness of pervasive games in creating immersive live-action game experiences principally depends on the correlation of the game content with actual physical elements. To address this issue, most pervasive game prototypes so far have been bound to specific locations, while game content has been manually edited by the developers; they have also been heavily dependent on the mediation of orchestration teams. Nevertheless, the capacity of pervasive games to be staged anywhere (i.e. their portability) is critical for their wider adoption and commercial success. Since the manual creation of game content is not feasible in portable games, UGC remains as the only practical option for content provision. Notably, the impact of UGC has not been studied so far in the pervasive games literature. This article introduces Barbarossa, a pervasive role-playing game based on UGC. Barbarossa serves as a testbed for investigating the effect of UGC under diverse technical, functional and game play characteristics. The user trials of Barbarossa confirmed that the effective use of UGC can enhance the quality of experience perceived by players and indirectly serve as a useful orchestration tool. We also document best practices with respect to the effective use of UGC in pervasive games, which could be useful to future developers.

Eliminating Unbounded Search in Computable Algebra

Abstract: Klaimullin, Melnikov and Ng [KMNa] have recently suggested a new systematic approach to algorithms in algebra which is intermediate between computationally feasible algebra [CR91, KNRS07] and abstract computable structure theory [AK00, EG00]. In this short survey we discuss some of the key results and ideas of this new topic [KMNa, KMNc, KMNb]. We also suggest several open problems.

Towards Computable Analysis on the Generalised Real Line

Abstract: In this paper we use infinitary Turing machines with tapes of length \(\kappa \) and which run for time \( \kappa \) as presented, e.g., by Koepke & Seyfferth, to generalise the notion of type two computability to \({2}^{\kappa }\), where \(\kappa \) is an uncountable cardinal with \(\kappa ^{<\kappa }=\kappa \). Then we start the study of the computational properties of \({{\mathrm{\mathbb {R}}}}_\kappa \), a real closed field extension of \({{\mathrm{\mathbb {R}}}}\) of cardinality \({2}^{\kappa }\), defined by the first author using surreal numbers and proposed as the candidate for generalising real analysis. In particular we introduce representations of \({{\mathrm{\mathbb {R}}}}_\kappa \) under which the field operations are computable. Finally we show that this framework is suitable for generalising the classical Weihrauch hierarchy. In particular we start the study of the computational strength of the generalised version of the Intermediate Value Theorem.

The “Horse” Inside: Seeking Causes Behind the Behaviors of Music Content Analysis Systems

Abstract: Building systems that possess the sensitivity and intelligence to identify and describe high-level attributes in music audio signals continues to be an elusive goal but one that surely has broad and deep implications for a wide variety of applications. Hundreds of articles have so far been published toward this goal, and great progress appears to have been made. Some systems produce remarkable accuracies at recognizing high-level semantic concepts, such as music style, genre, and mood. However, it might be that these numbers do not mean what they seem. In this article, we take a state-of-the-art music content analysis system and investigate what causes it to achieve exceptionally high performance in a benchmark music audio dataset. We dissect the system to understand its operation, determine its sensitivities and limitations, and predict the kinds of knowledge it could and could not possess about music. We perform a series of experiments to illuminate what the system has actually learned to do and to what extent it is performing the intended music listening task. Our results demonstrate how the initial manifestation of music intelligence in this state of the art can be deceptive. Our work provides constructive directions toward developing music content analysis systems that can address the music information and creation needs of real-world users.

What Makes People Watch Online Videos: An Exploratory Study

Abstract: Searching for and retrieving videos in a meaningful way on the web is still an open problem. The integration of a user's context and intentions into the search process is one of the most promising approaches to enhance current search interfaces and algorithms. In this article, we present the results of two exploratory studies on the topic of online video searching, retrieving, watching, and sharing: a qualitative study in which 22 participants reported on situations when they retrieved and watched videos, and an online quantitative survey with more than 200 participants answering comparable questions. We provide a detailed analysis of the results from both studies and report on the insights that they provide in terms of video search, retrieval, watching, and sharing behavior. Our findings can be used to enhance current video retrieval systems, search interfaces, and algorithms in order to improve the overall user satisfaction and experience. As an example of such improvements, we also propose a prototype that addresses the problem of taking the user's intentions into account when designing video retrieval interfaces.

Extending Wadge Theory to k-Partitions

Abstract: We extend some results about Wadge degrees of Borel subsets of Baire space to finite partitions of Baire space. A typical new result is the characterization up to isomorphism of the Wadge degrees of k-partitions with \(\mathbf {\Delta }^0_3\)-components.

Flexible Indexing of Repetitive Collections

Abstract: Highly repetitive strings are increasingly being amassed by genome sequencing experiments, and by versioned archives of source code and webpages. We describe practical data structures that support counting and locating all the exact occurrences of a pattern in a repetitive text, by combining the run-length encoded Burrows-Wheeler transform (RLBWT) with the boundaries of Lempel-Ziv 77 factors. One such variant uses an amount of space comparable to LZ77 indexes, but it answers count queries between two and four orders of magnitude faster than all LZ77 and hybrid index implementations, at the cost of slower locate queries. Combining the RLBWT with the compact directed acyclic word graph answers locate queries for short patterns between four and ten times faster than a version of the run-length compressed suffix array (RLCSA) that uses comparable memory, and with very short patterns our index achieves speedups even greater than ten with respect to RLCSA.

A One-Dimensional Physically Universal Cellular Automaton

Abstract: Physical universality of a cellular automaton was defined by Janzing in 2010 as the ability to implement an arbitrary transformation of spatial patterns. In 2014, Schaeffer gave a construction of a two-dimensional physically universal cellular automaton. We construct a one-dimensional version of the automaton and a reversibly universal automaton.

A BDI Game Master Agent for Computer Role-Playing Games

Abstract: In this paper we describe an approach for developing an intelligent game master (GM) for computer role-playing games. The role of the GM is to set up the game environment, manage the narrative ow and enforce the game rules whilst keeping the players engaged. Our approach is to use the popular Belief-Desire-Intention (BDI) model of agents to developing a GM. We describe the process for creating such a GM and how we implemented a prototype of it for a scenario in the Neverwinter Nights (NWN) game. We describe the evaluation of our prototype with human participants who played the chosen NWN scenario both with and without the BDI GM. The comparison survey completed by the participants shows that the system with the BDI GM was the clear winner with respect to game replayability, flexibility, objective setting and overall interest; thus, validating our hypothesis that a BDI GM will provide game players with a better gaming experience.

Permutive One-Way Cellular Automata and the Finiteness Problem for Automaton Groups

Abstract: The decidability of the finiteness problem for automaton groups is a well-studied open question on Mealy automata. We connect this question of algebraic nature to the periodicity problem of one-way cellular automata, a dynamical question known to be undecidable in the general case. We provide a first undecidability result on the dynamics of one-way permutive cellular automata, arguing in favor of the undecidability of the finiteness problem for reset Mealy automata.

Procedural Content Generation for Game Props? A Study on the Effects on User Experience

Abstract: This work demonstrates the potentials of procedural content generation (PCG) for games, focusing on the generation of specific graphic props (reefs) in an explorer game.We briefly portray the state-of-the-art of PCG and compare various methods to create random patterns at runtime. Taking a step towards the game industry, we describe an actual game production and provide a detailed pseudocode implementation showing how Perlin or Simplex noise can be used efficiently.In a comparative study, we investigate two alternative implementations of a decisive game prop: once created traditionally by artists and once generated by procedural algorithms. 41 test subjects played both implementations. The analysis shows that PCG can create a user experience that is significantly more realistic and at the same time perceived as more aesthetically pleasing. In addition, the ever-changing nature of the procedurally generated environments is preferred with high significance, especially by players aged 45 and above.

Stimulating Creative Partnerships in Human-Agent Musical Interaction

Abstract: Musical duets are a type of creative partnership with a long history of artistic practice. What can they tell us about creative partnerships between a human and a computer? To explore this question, we implemented an activity-based model of duet interaction in software designed to support musical metacreation and investigated the experience of performing with it. The activity-based model allowed for the application of reflexive interactive processes, previously used in dialogic interaction, to a synchronous musical performance context. The experience of improvising with the computational agent was evaluated by expert musicians, who reported that interactions were fun, engaging, and challenging, despite some obvious limitations in the musical sophistication of the software. These findings reinforce the idea that even simple metacreative systems can stimulate creative partnerships and, further, that creative human-machine duet partnerships may well produce, like human-human duet partnerships, more than the sum of their parts.

A Guided Tour to Computational Haplotyping

Abstract: Human genomes come in pairs: every individual inherits one version of the genome from the mother and another version from the father. Hence, every chromosome exists in two similar yet distinct “copies”, called haplotypes. The problem of determining the full sequences of both haplotypes is known as phasing or haplotyping. In this paper, we review different approaches for haplotyping and point out how they are formalized as optimization problems. We survey different technologies and, in this way, provide guidance on the characteristics of problem instances resulting from present day technologies. Furthermore, we highlight open algorithmic challenges.

On Higher Effective Descriptive Set Theory

Abstract: In the framework of computable topology, we propose an approach how to develop higher effective descriptive set theory. We introduce a wide class \(\mathbb {K}\) of effective \(T_0\)-spaces admitting Borel point recovering. For this class we propose the notion of an \((\alpha ,m)\)-retractive morphism that gives a great opportunity to extend classical results from EDST to the class \(\mathbb {K}\). We illustrate this by several examples.

Surjective H-Colouring: New Hardness Results

Abstract: A homomorphism from a graph G to a graph H is a vertex mapping f from the vertex set of G to the vertex set of H such that there is an edge between vertices f(u) and f(v) of H whenever there is an edge between vertices u and v of G. The H-Colouring problem is to decide whether or not a graph G allows a homomorphism to a fixed graph H. We continue a study on a variant of this problem, namely the Surjective \(H\)-Colouring problem, which imposes the homomorphism to be vertex-surjective. We build upon previous results and show that this problem is NP-complete for every connected graph H that has exactly two vertices with a self-loop as long as these two vertices are not adjacent. As a result, we can classify the computational complexity of Surjective \(H\)-Colouring for every graph H on at most four vertices.

Scaling Online Games with NetConnectors: A Peer-to-Peer Overlay for Fast-Paced Massively Multiplayer Online Games

Abstract: This article presents a peer-to-peer overlay for massively multiplayer online games with a focus on fast-paced action. More than other genres, action games like first-person shooters employ fast and dynamic game mechanics. In multiplayer environments, these properties have to be reflected by the underlying network structure. At the same time, the system should be able to support a huge amount of users in order to deliver a massive experience to the participating players. The capacity of current client/server systems limits the number of players in a game, preventing the desired massive experience.To provide both a scalable and a responsive system, we use a fully distributed peer-to-peer network with a dynamic connection scheme. By exploiting local interests in the virtual world, our system supports a huge number of users. Therefore, an area-of-interest mechanism is applied to the connection scheme. Users do not connect to all participating users, but they only establish connections to other users they are interested in. These neighbors are determined by the user's perception of the virtual world. Instead of using a purely distance-based approach, our system uses a more flexible neighbor-based approach that supports the use of multiple metrics to determine the set of interesting nodes for each user. A second kind of connection—so-called NetConnectors—utilizes the players' distribution in the virtual world to ensure overlay consistency. For the dissemination of messages, we use a publish/subscribe mechanism. This prevents inconsistencies introduced by unidirectional neighborhood relations that can occur with sender-oriented models. Further, the publish/subscribe mechanism models the users' interests more accurately. In addition to the regular sending mechanism, we implemented a Geocast algorithm that allows information distribution to arbitrary regions of the virtual world. While regular messages are always addressed to specific users, Geocasts cover certain geographical regions. Thus, Geocasts can be used to disseminate messages to all users that are located in the addressed region.Simulations show that our design performs well in terms of scalability. By keeping the amount of connections per user nearly constant, users do not get overloaded with too many connections. This also applies for crowded regions where the user density is much higher compared to an evenly populated virtual world. Another important aspect of fast-paced multiplayer games is the users' motion behavior. Different movement strategies are evaluated for their impact on network load and connection dynamics.

Augmented Reality Enriches Print Media and Revitalizes Media Business

Abstract: Print media is in a crisis; it is losing its share of advertising—its main source of income—to digital media. Our aim is to determine how augmented reality (AR) and other hybrid media solutions change print media's value chain and what kind of opportunities they offer. We studied both human and technical aspects and critical challenges. We interviewed 20 actors of Finnish advertising and media business, who are very enthusiastic toward AR-enriched interactive hybrid media. User behavior measurability was found to be important. We present a sketch of the hybrid media value chain with the actors. We also describe and discuss selected AR applications. AR technology is mature enough for the mass market; the technical performance of smartphones is high enough for AR applications, and the penetration of smartphones is increasing rapidly. Our main conclusion is that hybrid media is essential to the future of print media.

Koepke Machines and Satisfiability for Infinitary Propositional Languages

Abstract: We consider complexity theory for Koepke machines, also known as Ordinal Turing Machines (OTMs), and define infinitary complexity classes \(\infty \)-\(\mathbf {P}\) and \(\infty {\text {-}}\mathbf {NP}\) and the OTM analogue of the satisfiability problem, denoted by \(\infty {\text {-}}\mathrm {SAT}\). We show that \(\infty {\text {-}}\mathrm {SAT}\) is in \(\infty {\text {-}}\mathbf {NP}\) and \(\infty {\text {-}}\mathbf {NP}\)-hard (i.e., the problem is \(\infty {\text {-}}\mathbf {NP}\)-complete), but not OTM decidable.

Admissibles in Gaps

Abstract: We consider clockable ordinals for Infinite Time Turing Machines (ITTMs), i.e., halting times of ITTMs on the empty input. It is well-known that, in contrast to the writable ordinals, the set of clockable ordinals has ‘gaps’. In this paper, we show several results on gaps, mainly related to the admissible ordinals they may properly contain. We prove that any writable ordinal can occur as the order type of the sequence of admissible ordinals in such a gap. We give precise information on their ending points. We also investigate higher rank ordinals (recursively inaccessible, etc.). Moreover, we show that those gaps can have any reasonably effective length (in the sense of ITTMs) compared to their starting point.

Strategies and Challenges to Facilitate Situated Learning in Virtual Worlds Post-Second Life

Abstract: Virtual worlds can establish a stimulating environment to support a situated learning approach in which students simulate a task within a safe environment. While in previous years Second Life played a major role in providing such a virtual environment, there are now more and more alternative—often OpenSim-based—solutions deployed within the educational community. By drawing parallels to social networks, we discuss two aspects: how to link individually hosted virtual worlds together in order to implement context for immersion and how to identify and avoid “fake” avatars so people behind these avatars can be held accountable for their actions.

Turing’s 1949 Paper in Context

Abstract: Anyone who has written one knows how frustratingly difficult it can be to perfect a computer program. Some of the founding fathers of computing set out ideas for reasoning about software — one would say today ‘techniques for proving that a program satisfies its specification’. Alan Turing presented a paper entitled Checking a Large Routine that laid out a workable method for reasoning about programs. Sadly his paper had little impact. Understanding the problem faced, Turing’s proposal and what followed provides insight into how ideas evolve. Comparing three contributions from the 1940s with the current state of the art clarifies a problem that still costs society a fortune each year.

Formalizing a Fragment of Combinatorics on Words

Abstract: We describe an attempt to formalize some tasks in combinatorics on words using the assistance of Prover9, an automated theorem prover for first-order and equational logic.

Preserving the Motion Features in Nonavoiding Collision Crowds

Abstract: In current games, entire cities can be rendered in real time into massive virtual worlds. In addition to the enormous details of geometry, rendering, effects (e.g., particles), sound effects, and so on, nonplayable characters must also be animated and rendered, and they must interact with the environment and among themselves. Indeed, the computation time of all such data is expensive. Consequently, game designers should define priorities so that more resources can be allocated to generate better graphics, setting aside behavioral aspects. In huge environments, some of the actions/behaviors that should be processed can be nonvisible to the players (occluded) or even visible but far away. Normally, in such cases, the common decision is to turn off such processing. However, hidden enemy behaviors that are not processed can result in nonrealistic feedback to the player. In this article, we aim to provide a method to preserve the motion of nonvisible characters while maintaining a compromise with the needed computational time of background behaviors. We apply this idea specifically in crowd collision behavior, proposing nonavoiding collision crowds. Such crowds do not have collision avoidance behaviors but preserve their motion as typical crowds. We propose a mathematical technique to describe how people are affected by others, so collision avoidance methods are not necessarily computed (they can be turned off, which leads to a reduction in the required computational time). Results show that our method replicates the behavior well (velocities, densities, and time) when compared to a free-of-collision method.

Degrees of Categoricity of Rigid Structures

Abstract: We prove that there exists a properly 2-c.e. Turing degree \(\mathbf{d}\) which cannot be a degree of categoricity of a rigid structure.

Supporting Team Work in Game Design: Better - Better Team Relationships

Abstract: Developing a video game is a costly activity, not only from an economic perspective, but also in terms of the time devoted to researching innovative solutions and managing interfaces between the creative and technical team members. In this article, we explore the possibility to use an approach rooted into AI techniques (namely Behaviour Trees) to help establish a lingua franca between these two different functions, in order to optimize both the development time and the quality of the final product. In particular, we have developed BETTER, a middleware which can be easily embedded into any game engine, and tested it during the design and development of Crazy-Hill, a commercial video game for iOS-based mobile devices.