In this paper we discuss the task of dialogue act recognition as a part of interpreting user utterances in context. To deal with the uncertainty that is inherent in natural language processing in general and dialogue act recognition in particular we use machine learning techniques to train classifiers from corpus data. These classifiers make use of both lexical features of the (Dutch) keyboard-typed utterances in the corpus used, and context features in the form of dialogue acts of previous utterances. In particular, we consider probabilistic models in the form of Bayesian networks to be proposed as a more general framework for dealing with uncertainty in the dialogue modelling process.

The development of quantum walks in the context of quantum computation, as generalisations of random walk techniques, has led rapidly to several new quantum algorithms. These all follow a unitary quantum evolution, apart from the final measurement. Since logical qubits in a quantum computer must be protected from decoherence by error correction, there is no need to consider decoherence at the level of algorithms. Nonetheless, enlarging the range of quantum dynamics to include non-unitary evolution provides a wider range of possibilities for tuning the properties of quantum walks. For example, small amounts of decoherence in a quantum walk on the line can produce more uniform spreading (a top-hat distribution), without losing the quantum speed up. This paper reviews the work on decoherence, and more generally on non-unitary evolution, in quantum walks and suggests what future questions might prove interesting to pursue in this area.

Quantum physics, together with the experimental (and slightly controversial) quantum computing, induces a twist in our vision of computation, and hence, since computing and logic are intimately linked, in our approach to logic and foundations. In this paper, we discuss the most mistreated notion of logic, truth.

This special issue of Mathematical Structures in Computer Science contains several contributions related to the modern field of Quantum Information and Quantum Computing.

The first two papers deal with entanglement. The paper by R. Mosseri and P. Ribeiro presents a detailed description of the two- and three-qubit geometry in Hilbert space, dealing with the geometry of fibrations and discrete geometry. The paper by J.-G.Luque et al. is more algebraic and considers invariants of pure k-qubit states and their application to entanglement measurement.

In the longstanding debate in political economy about the feasibility of socialism, the Austrian School of Economists have argued that markets are an indispensable means of evaluating goods, hence a prerequisite for productive efficiency. Socialist models for non-market economic calculation have been strongly influenced by the equilibrium model of neoclassical economics. The Austrians contend that these models overlook the essence of the calculation problem by assuming the availability of knowledge that can be acquired only through the market process itself. But the debate in political economy has not yet considered the recent emergence of agent-based systems and their applications to resource allocation problems. Agent-based simulations of market exchange offer a promising approach to fulfilling the dynamic functions of knowledge encapsulation and discovery that the Austrians show to be performed by markets. Further research is needed in order to develop an agent-based approach to the calculation problem, as it is formulated by the Austrians. Given that the macro-level objectives of agent-based systems can be easily engineered, they could even become a desirable alternative to the real markets that the Austrians favour.

Pervasive computing is by its nature open and extensible, and must integrate the information from a diverse range of sources. This leads to a problem of information exchange, so sub-systems must agree on shared representations. Ontologies potentially provide a well-founded mechanism for the representation and exchange of such structured information. A number of ontologies have been developed specifically for use in pervasive computing, none of which appears to cover adequately the space of concerns applicable to application designers. We compare and contrast the most popular ontologies, evaluating them against the system challenges generally recognized within the pervasive computing community. We identify a number of deficiencies that must be addressed in order to apply the ontological techniques successfully to next-generation pervasive systems.

We give an algorithm allowing the construction of bases of local unitary invariants of pure k-qubit states from a knowledge of the polynomial covariants of the group of invertible local filtering operations. The simplest invariants obtained in this way are made explicit and compared with various known entanglement measures. Complete sets of generators are obtained for up to four qubits, and the structure of the invariant algebras is discussed in detail.

This paper reviews recent work related to the interplay between quantum information and computation on the one hand and classical and quantum chaos on the other.

First, we present several models of quantum chaos that can be simulated efficiently on a quantum computer. Then a discussion of information extraction shows that such models can give rise to complete algorithms including measurements that can achieve an increase in speed compared with classical computation. It is also shown that models of classical chaos can be simulated efficiently on a quantum computer, and again information can be extracted efficiently from the final wave function. The total gain can be exponential or polynomial, depending on the model chosen and the observable measured. The simulation of such systems is also economical in the number of qubits, allowing implementation on present-day quantum computers, some of these algorithms having been already experimentally implemented.

The second topic considered concerns the analysis of errors on quantum computers. It is shown that quantum chaos algorithms can be used to explore the effect of errors on quantum algorithms, such as random unitary errors or dissipative errors. Furthermore, the tools of quantum chaos allows a direct analysis of the effects of static errors on quantum computers. Finally, we consider the different resources used by quantum information, and show that quantum chaos has some precise consequences on entanglement generation, which becomes close to maximal. For another resource, interference, a proposal is presented for quantifying it, enabling a discussion on entanglement and interference generation in quantum algorithms.

This paper reviews recent attempts to describe the two- and three-qubit Hilbert space geometries. In the first part, this is done with the help of Hopf fibrations of hyperspheres. It is shown that the associated Hopf map is strongly sensitive to states’ entanglement content. In the two-qubit case, a generalisation of the celebrated one-qubit Bloch sphere representation is described. In the second part, we present Hilbert space discrete versions, which are comparable to polyhedral approximations of spheres in standard geometry.

The technological changes of the twentieth century obliged research institutes to rethink their role in society. A place for invention and reflection, and a centre for the preservation of our musical heritage, the Groupe de Recherches Musicales must open its doors from now on and increase its collaboration with other bodies in an enlarged form: an extended ‘group’, extramural, which shares its tools and thoughts with others.

Sixty years ago, musique concrète was born of the single-handed efforts of one man, Pierre Schaeffer. How did the first experiments become a School and produce so many rich works? As this issue of Organised Sound addresses various aspects of the GRM activities throughout sixty years of musical adventure, this article discusses the musical thoughts behind the advent and the development of the music created and theoretised at the Paris School formed by the Schaefferian endeavours. Particular attention is given to the early twentieth-century conceptions of musical sounds and how poets, artists and musicians were expressing their quest for, as Apollinaire put it, ‘new sounds new sounds new sounds’. The questions of naming, gesture, sound capture, processing and diffusion are part of the concepts thoroughly revisited by the GRMC, then the GRM in 1958, up to what is known as acousmatic music. Other contributions, such as Teruggi's, give readers insight into the technical environments and innovations that took place at the GRM. This present article focuses on the remarkable unity of the GRM. This unity has existed alongside sixty years of activity and dialogue with researchers of other fields and constant attention to the latter-day scientific, technological and philosophical ideas which have had a strong influence in shaping the development of GRM over the course of its history.

It is a habit to invoke Aristotle when dealing, within the arts, with ‘Nature’ – that the Man–Artist (and not only the musician) would be, he says, ‘inclined’ to imitate. It is true, the history of music clearly attests to the temptation and of the ‘pleasure’ (as Aristotle also says) found in mimesis. We know that very lately in history musique concrète gives a new perspective to this question as well as to other questions, and changes the deal: because the sound objects of the world, of the whole world – the ‘noises’ – that needed to be imitated, can now be easily captured through technology, almost in a photographic way, and then they can be gathered, kept, and finally be composed. Hopefully Pierre Schaeffer, its genial inventor, has, concerning the question of nature within new music, a position that tears him apart, which is paradoxical, uncomfortable, fundamental: that the nature that is so easily captured, he does not want to exhibit; to understand the lessons, the hidden musical lessons, he only wants to examine it. This almost heroic model will only be partially followed by the composers (concrète, electroacoustic, acousmatic, anecdotical composers) who have been working during the last sixty years in this passionate domain. At the end of this article, the sketch of a typology, based on musical examples, tries to clarify the way nature is dealt with, when it appears in musique concrète.

When studying the history and evolution of the GRM, one of its outstanding features has been its continuous energy dedicated to developing machines, systems and, in recent years, software that would better serve composers' views and intentions. Unique discoveries were made that have become the fundamental concepts of sound manipulation and have influenced researchers and developers in the conception of new, but always somehow faithful to the original, tools for composition. Many steps pave this road, some are known and recognised, others were necessary failures that permitted inventors to re-focus and realise their thoughts.

Among the questions regularly put to me, those that recur most often touch upon three aspects, three things to consider that are, truth to tell, unending within the domain of organised sounds. Those questions that take the lead are usually concerned with space – the representation of space as well as the production of space. Then come those that deal with listening, active or passive. Last are those relating to tools for making and for listening. Together, these approaches run through the stages that are very natural in position problematics: where, when, how, for whom, why? I would like, in formulating these repeated questions once more, to make myself re-orientate them in such a way to show that by bringing to bear forty years of experience, I have tried to reply to them as much through practice as through theory, putting forward the idea of a family of operational concepts linked together through the perceptual radical ‘acous’: acousmatic, acousmonium, acousmographe, acousmathèque.

An interview is a strange format for a research review; however, it is sometimes a quick and effective way to present a problematic. In this case, Christian Zanési interviewed by Évelyne Gayou gives a perspective of the future activities of the GRM from an institutional perspective as well as in relation with the new electronic tendencies, thus answering the major question of the social function of a research and production institution today.

The year 1958 witnessed the birth of the institution GRM, nurtured by the French Radio and Television service (RTF). However, the fifty years of the GRM cannot be dissociated from the preceding period, datable from 1942, when Pierre Schaeffer began experiments with radiophonic sound which led him to musique concrète while bringing into existence the institutional infrastructure of the group. We can therefore see the Studio d'Essai (1942–46), the Club d'Essai (1946–60) with its Groupe de Recherche de Musique Concrète (GRMC, 1951–58) as forebears of the GRM. The fundamental principle, which lies in working with sonic material directly on the recording media through a precise listening to recorded elements, led Schaeffer to affirm that there is another way to access music other than from notation.

He used this powerful idea as the fixed point on the compass for all his research. Linked from its origins to the broadcasting services – RTF until 1964, ORTF up to 1974, then INA ever since – the GRM has constantly adapted its theories and its ideas to successive technological developments: smooth disks (shellac records), magnetic tape, computer memory. A fruitful period at the Service de la Recherche (1960–75) allowed Schaeffer and his team to systematically examine the world of sounds from their own listening experience. The Traité des Objets Musicaux (Treatise of Musical Objects) bears witness to this research. Since 1975 another adventure has been under way: that of the preservation and making available of works and discoveries gathered over the years – an exceptional heritage which continues to grow and interest an ever larger public.

This article presents a detailed analysis of Christian Zanesi's work, Arkhéion, Les voix de Pierre Schaeffer. The main structuring ideas as well as a description of the materials used is presented, thus stressing the opposition between horizontal and vertical trends in time. The presence of the voice of Pierre Schaeffer gives the work a particular introspection through its relation to the life of Schaeffer and his ideas.

In order to understand through the original writings the evolution of ideas and technology in the history of GRM, a recommended bibliography is proposed here.