Daimi Reports

 

Since 2001 the annual Danish Human-Computer Interaction Research Symposium has been a platform for networking, and provided an opportunity to get an overview across the various parts of the Danish HCI research scene.

 

This booklet contains the proceedings of the Tenth Workshop on Practical Use of Coloured Petri Nets and the CPN Tools, October 19-21, 2009. The workshop is organised by the CPN group at the Department of Computer Science, Aarhus University, Denmark. The papers are also available in electronic form via the web pages:
http://www.cs.au.dk/CPnets/workshop09

 

Typically, objects are monolithic entities with a fixed interface. To increase the flexibility in this area, this paper presents first-class object sets as a language construct. An object set offers an interface which is a disjoint union of the interfaces of its member objects. It may also be used for a special kind of method invocation involving multiple objects in a dynamic look-up process. With support for feature access and late-bound method calls object sets are similar to ordinary objects, only more flexible. The approach is made precise by means of a small calculus, and the soundness of its type system is shown by a mechanically checked proof in Coq.

 

This booklet contains the proceedings of the Ninth Workshop on Practical Use of Coloured Petri Nets and the CPN Tools, October 20-22, 2008. The workshop is organised by the CPN group at the Department of Computer Science, University of Aarhus, Denmark. The papers are also available in electronic form via the web pages:
http://www.daimi.au.dk/CPnets/workshop08

 

This report describes the design and implementation of a mobile, peer-to-peer, remote execution system called Scavenger. A peer running Scavenger is capable of automatically discovering available, unused computing resources in its vicinity and, by means of mobile code, utilizing these resources to its own good.

 

This project is the written report for the course in Picture Processing at Aarhus University. The starting point is a paper by Michael Leyton in Artificial Intelligence, 1988: A Process Grammar for Shape. The paper describes how it is possible to derive the process history for an object from its state at two stages in its development. The aim in this project is to describe and test an algorithm for doing this.

 

In the resilient memory model any memory cell can get corrupted at any time, and corrupted cells cannot be distinguished from uncorrupted cells. An upper bound on the number of corruptions and O(1) reliable memory cells are provided.

 

This booklet contains the proceedings of the Eighth Workshop on Practical Use of Coloured Petri Nets and the CPN Tools, October 22-24, 2007. The workshop is organised by the CPN group at the Department of Computer Science, University of Aarhus, Denmark. The papers are also available in electronic form via the web pages:
http://www.daimi.au.dk/CPnets/workshop07

 

In cancer treatment organ and tissue deformation between radiotherapy sessions represent a significant challenge to optimal planning and delivery of radiation doses. Recent developments in image guided radiotherapy has caused a sound request for more advanced approaches for image registration to handle these deformations. Viscous fluid registration is one such deformable registration method. This paper demonstrates that the GPU can be used to drastically reduce the time needed to register two medical 3D images using the viscous-fluid registration method.

 

In mobile and ubiquitous computing the location of devices is often important both for the behaviour of the applications and for communication and other middleware functionality. Mobility prediction enables proactively dealing with changes in location dependent functionality. In this project the ability of Bayesian networks to reason on the basis of incomplete or inaccurate information is powering mobility prediction based on a street map and the current location and direction of the vehicle.

 

This is a book of abstracts from the workshop on Multiple and Ubiquitous Interaction, 28.-30. March 2007.

 

Since 2001 the annual Danish Human-Computer Interaction Research Symposium has been a platform for networking, and provided an opportunity to get an overview across the various parts of the Danish HCI research scene. For this years symposium we received a record number of 28 submissions.

 

The individual papers from this workshop can be found at
http://www.daimi.au.dk/CPnets/workshop06/cpn/papers/

 

Type abstraction in object-oriented languages embody two techniques, each with its own strenghts and weaknesses. The first technique is extension, yielding abstraction mechanisms with good support for gradual specification. The prime example is inheritance. The second technique is functional abstraction, yielding more precise knowledge about the outcome. The prime example is type parameterized classes. This paper argues that these techniques should be clearly separated to work optimally, and also that current languages fail to do this.
We have applied this design philosophy to a language based on an extension mechanism, namely virtual classes. As a result, some elements based on functional abstraction have been introduced, but they are simple and only used for things where they excel; conversely, the virtual classes have become more flexible, because their role is now more well-defined. We designate the result as family genericity.
The presented language design has been implemented.

 

Virtual classes are class-valued attributes of objects. Like virtual methods, virtual classes are defined in an object's class and may be redefined within subclasses. They resemble inner classes, which are also defined within a class, but virtual classes are accessed through object instances, not as static components of a class. When used as types, virtual classes depend upon object identity – each object instance introduces a new family of virtual class types. Virtual classes support large-scale program composition techniques, including higher-order hierarchies and family polymorphism. The original definition of virtual classes in BETA left open the question of static type safety, since some type errors were not caught until runtime. Later the languages Caesar and gbeta have used a more strict static analysis in order to ensure static type safety. However, the existence of a sound, statically typed model for virtual classes has been a long-standing open question. This paper presents a virtual class calculus, vc, that captures the essence of virtual classes in these full-fledged programming languages. The key contributions of the paper are a formalization of the dynamic and static semantics of vc and a proof of the soundness of vc.

 

This booklet contains the proceedings of the workshop organized by the CPN group at Department of Computer Science, University of Aarhus, Denmark. The papers are also available in electronic form via the web pages:
http://www.daimi.au.dk/CPnets/workshop05

 

This report describes the hierarchical maps used as a central data structure in the Corundum framework. We describe its most prominent features, argue for its usefulness and briefly describe some of the software prototypes implemented using the technology.

 

This volume consists of revised papers from the First International Workshop on Activity Theory Based Practical Methods for IT Design. The workshop took place in Copenhagen, Denmark, September 2-3, 2004. The particular focus of the workshop was the development of methods based on activity theory for practical development of IT-based systems.

 

The LIWAS Traffic Warning System aims at providing early warning to vehicles about slippery conditions on the road. The LIWAS system is currently under development and consists of two main parts: sensors for measuring and classifying the state of the road, and a communication infrastructure for distributing road-state information to vehicles. This paper concentrates on the communication infrastructure and considers the application of zone flooding for implementing the distribution of road-state information. Zone flooding combines flooding and geocasting to distribute road-state information in a geographically bounded area. To evaluate the applicability of zone flooding in the LIWAS system a simulation model has been created using the Network Simulator 2. The simulation model captures a representative road scenario and has been used to evaluate several flooding protocols when used to implement zone flooding. The primary evaluation criteria are the load on the network and the capability to warn other vehicles in time.

 

This report is the Proceedings of the NordiCHI 2004 Workshop held in Tampere, Finland on October 24, 2004.

 

This booklet contains the proceedings of the 'Third International Workshop on Modelling of Objects, Components, and Agents' (MOCA04), October 11-13, 2004. The workshop is organised by the 'Coloured Petri Nets' group at the Department of Computer Science, University of Aarhus, Denmark, and the 'Theoretical Foundations of Computer Science' group at the University of Hamburg, Germany. The homepage of the workshop is: http://www.daimi.au.dk/CPnets/workshop04

 

This booklet contains the proceedings of the Fifth Workshop on Practical Use of Coloured Petri Nets and the CPN Tools, October 8-11, 2004. The workshop is organised by the CPN group at the Department of Computer Science, University of Aarhus, Denmark. The papers are also available in electronic form via the web pages: http//www.daimi.au.dk/CPnets/workshop04

 

The use of partial evaluation for specializing programs written in imperative languages such as C and Java is hampered by the difficulty of controlling the specialization process. We have developed a simple declarative language for controlling the specialization of Java programs and interfaced this language with the JSpec partial evaluator for Java. This language, named Pesto, allows declarative specialization of programs written in an object-oriented style of programming. The Pesto compiler automatically generates guards that enable the specialized code in the right context.

 

A new Bang & Olufsen system is installed in the living room of Paul and Sarah. The B&O sales people do the technical set-up, demonstrate the functionality of the new system for Paul and Sarah, and leave them to explore their new wonder. Not an unusual situation, but nevertheless a situation which fosters a set of concerns at B&O and indeed also for the field of Human Computer Interaction. B&O is concerned with making sure that their customers find B&O systems intuitive to use and over time learn to use the facilities offered by the system. Looking to the field of Human-Computer Interaction, this situation raises more questions than can be answered. These questions drive the work reported in this thesis.
The thesis deals with three general challenges for the area of Human-Computer Interaction. First, it investigates the consequences of the proliferation of computers from the workplace into our everyday lives. Secondly it examines the theoretical and practical implications of considering learning-in-use, as opposed to more static views on technology use. Finally, it examines how we can come to design for learning in use of everyday artefacts, i.e. it aims at approaching the first challenges from a design perspective.
The work presented in the following comes out of a tradition of action-oriented research. Thus the above problems emerged through collaboration with the interaction design group at Bang & Olufsen. The empirical part of the thesis consists of a long-term study of Bang & Olufsen television use in the home of two families. Furthermore, design workshops have been held with families in their homes, and experiments with design practice have been organised together with Bang & Olufsen. Theoretically, activity theory is explored as a basis for understanding learning-in-use. On this basis, a framework of learning artefacts is developed, and this framework is used to analyse the long-term study of B&O use.
The main contributions of this thesis is the framework of learning artefacts and a set of design principles for everyday artefacts, developed on the basis of this framework. In addition, it presents a further development of the perspective of design and use as strongly related and provides an example of how the framework of learning artefacts allow us to evaluate design, not only against use but also against the design practice, which produced it. Finally, the thesis offers a methodological cycle for designing for learning in use and the methods and techniques developed as part of this thesis are framed herein.

 

The Program Visualization Workshops aim to bring together researchers who design and construct program visualizations and, above all, educators who use and evaluate visualizations in their teaching. The first workshop took place in July 2000 at Porvoo, Finland. The second workshop was held in cooperation with ACM SIGCSE and took place at HornstrupCentret, Denmark in June 2002, immediately following the ITiCSE 2002 Conference in Aarhus, Denmark.

 

Inheritance allows a class to be specialized and its attributes refined, but implementation specialization can only take place by overriding with manually implemented methods. Automatic program specialization can generate a specialized, efficient implementation. However, specialization of programs and specialization of classes (inheritance) are considered different abstractions. We present a new programming language, Lapis, that unifies inheritance and program specialization at the conceptual, syntactic, and semantic levels.
This paper presents the initial development of Lapis, which uses inheritance with covariant specialization to control the automatic application of program specialization to class members. Lapis integrates object-oriented concepts, block structure, and techniques from automatic program specialization to provide both a language where object-oriented designs can be efficiently implemented and a simple yet powerful partial evaluator for an object-oriented language.

 

This PhD dissertation deals with how to design mobile technology to support mobile work. More specifically, I have worked with the following three connected components: design (as process as well as tool), mobile work (specifically on process plants), and technology (mobile and stationary and the relationship between them).
I define the relationship between these three components based on the action-oriented research approach known as the Scandinavian tradition for systems development, which has grounded and shaped my research method. Cooperation, active user involvement and experimental development of methods and techniques are key elements in this approach, and are elements I develop further in a mobile work environment. Another influencing factor on my approach to the mobile work domain is the current technical development: of the staggering number of microchips produced annually, only a small fraction is being used for Personal Computers the rest are used in mobile and embedded technology. Thus we are dealing with an entirely new range of technology, possibilities and limitations, and consequently new user interface challenges.
Based on this, I see the following key connections to design of technological support of mobile work in a process setting: the design process and the usability methods we use create an understanding of the work practice and the work situations we are trying to support with new technology. The work practise and specific tasks set the boundaries for what we support and how we go about it, and particularly in a mobile work context it is important to understand the heterogeneity in the work: the work tasks and the available resources change in relation to where you are (at the home office, at the site of a client, amongst the machines in the plant) and the users' needs for technological support and access to information changes accordingly. These relationships must be reflected in the technology we design, and it is thus often in a mobile work context more relevant to create a selection of different technological tools for the users to choose between as their needs change, than by replacing one technological approach or device with another. This bears particular importance in relation to mobile technology as the handheld device often supports the mobility but sacrifices the sense of overview because the physically small screens are unable to support it as well as a large PC monitor.
Consequently, the relationship between the three elements is an important aspect of my PhD dissertation. I deal with how mobile work makes new demands on the technological devices we design to support it, thereof mobile technology. I also deal with how the mobile artefacts demand new thinking in relation to the user interface design and functionality because we are dealing with a new type of technology, not just a very small PC with limited screen and next to no peripherals. Finally, I deal with how this new area of research (and the development of HCI and usability in general) sets new demands for the usability methods, how and to what degree we involve users and other professionals in design, how we take advantage of the use environment and utilise the use context actively in the design process.
As a collective concept for the development of mobile technology to support mobile work, I introduce the `web-of-technology' concept that requires we create an understanding of which role the new device should play in relation to the already existing technology in the specific work domain. By placing the new, hand-held technology in the existing `web-of-technology' you are forced to analyse which relations the mobile device should have to the other technological devices in the work context and whether the mobile artefact should be strongly, weakly, or not integrated with the other technology at all. The degree of integration between technologies affects the design of both the functionality and the user interface; strongly integrated devices demand a large degree of visual and functional consistency across devices. It is thus essential that we clarify these questions of the technology that is and the technology that will be early in the design process, just as naturally as we examine how the work practice affects the development and design.

 

This booklet is the author's PhD-dissertation.

 

This booklet is the author's PhD-dissertation.

 

This booklet is the author's PhD-dissertation.

 

This report contains the proceedings of the workshop Modelling of Objects, Components, and Agents (MOCA'02), August 26-27, 2002.The workshop is organized by the 'Coloured Petri Net' Group at the University of Aarhus, Denmark and the 'Theoretical Foundations of Computer Science' Group at the University of Hamburg, Germany. The homepage of the workshop is: http://www.daimi.au.dk/CPnets/workshop02/

 

This booklet contains the proceedings of the Fourth Workshop on Practical Use of Coloured Petri Nets and the CPN Tools, August 28-30, 2002. The workshop is organised by the CPN group at the Department of Computer Science, University of Aarhus, Denmark. The papers are also available in electronic form via the web pages: http://www.daimi.au.dk/CPnets/workshop02

 

This thesis examines object-oriented modelling in experimental system development. Object-oriented modelling aims at representing concepts and phenomena of a problem domain in terms of classes and objects. Experimental system development seeks active experimentation in a system development project through, e.g., technical prototyping and active user involvement. We introduce and examine "experimental object-oriented modelling" as the intersection of these practices.

 

Crank-Nicolson is a popular method for solving parabolic equations because it is unconditionally stable and second order accurate. One drawback of CN is that it responds to jump discontinuities in the initial conditions with oscillations which are weakly damped and therefore may persist for a long time. We present a selection of methods to reduce the amplitude of these oscillations.

 

The procedure call mechanism has conquered the world of programming, with object-oriented method invocation being a procedure call in context of an object. This paper presents an alternative, method mixin invocations, that is optimized for flexible creation of composite behavior, where traditional invocation is optimized for as-is reuse of existing behavior.

Tight coupling reduces flexibility, and traditional invocation tightly couples transfer of information and transfer of control. Method mixins decouple these two kinds of transfer, thereby opening the doors for new kinds of abstraction and reuse. Method mixins use shared name spaces to transfer information between caller and callee, as opposed to traditional invocation which uses parameters and returned results. This relieves a caller from dependencies on the callee, and it allows direct transfer of information further down the call stack, e.g. to a callee's callee.

The mechanism has been implemented in the programming language gbeta. Variants of the mechanism could be added to almost any programming language with mutable state.

 

Combination of descriptive entities--i.e. multiple inheritance and related mechanisms--is usually only supported at compile time in statically typed languages. The language gbeta is statically typed and has supported run-time creation of classes and methods since 1997, by means of the pattern combination operator '&'. However, with certain combinations of operands the '&' operator fails; as a result, creation of new classes and methods at run-time had to be considered a dangerous operation. This paper presents a large and useful class of combinations, and proves that combinations in this class will always succeed.

 

"The First Danish Human-Computer Interaction Research Symposium has been realised as a joint effort between sigchi.dk and Centre for Human-Machine Interaction. The primary motivation for this effort has been to stimulate networking and to create an overview of recent Danish HCI research. The present proceedings consist of the 25 extended abstracts accepted for the symposium, presenting a very broad range of work, characteristic for Danish HCI research. In addition, 3 thesis (in progress) summaries from the doctoral colloquium are included."

 

This booklet contains the proceedings of the Third Workshop on Practical Use of Coloured Petri Nets and the CPN Tools, August 29-31, 2001. The workshop is organised by the CPN group at Department of Computer Science, University of Aarhus, Denmark. The papers are also available in electronic form via the web pages: http://www.daimi.au.dk/CPnets/workshop01/

 

This booklet contains the proceedings of the workshop Modelling of Objects, Components, and Agents (MOCA'01), August 27-28, 2001. The workshop is organised by the CPN group at the Department of Computer Science, University of Aarhus, Denmark and the "Theoretical Foundations of Computer Science" Group at the University of Hamburg, Germany. The papers are also available in electronic form via the web pages: http://www.daimi.au.dk/CPnets/workshop01/

 

Object-oriented programming facilitates the development of generic software, but at a cost in terms of performance of the final program. We use partial evaluation to automatically map generic object-oriented software into specific implementations. In this paper we give a concise and formalized description of how partial evaluation specializes an object-oriented program.

 

The object-oriented style of programming facilitates program adaptation and enhances program genericness, but at the expense of efficiency. We demonstrate experimentally that state-of-the-art Java compilation technology fails to compensate for the use of object-oriented abstractions to implement generic programs, and that program specialization can be used to eliminate these overheads. We present an automatic program specializer for Java, and demonstrate experimentally that significant speedups in program execution time can be obtained through automatic specialization. Although automatic program specialization could be seen as overlapping with existing optimizer compiler technology, we show that specialization and compiler optimization are in fact complementary.

 

The most important theoretical tool in connection with machine learning is the bias/variance decomposition of error functions. Together with Tom Heskes, I have found the family of error functions with a natural bias/variance decomposition that has target independent variance. It is shown that no other group of error functions can be decomposed in the same way. An open problem in the machine learning community is thereby solved. The error functions are derived from the deviance measure on distributions in the one-parameter exponential family. It is therefore called the deviance error family.

A bias/variance decomposition can also be viewed as an ambiguity decomposition for an ensemble method. The family of error functions with a natural bias/variance decomposition that has target independent variance can therefore be of use in connection with ensemble methods.

The logarithmic opinion pool ensemble method has been developed together with Anders Krogh. It is based on the logarithmic opinion pool ambiguity decomposition using the Kullback-Leibler error function. It has been extended to the cross-validation logarithmic opinion pool ensemble method. The advantage of the cross-validation logarithmic opinion pool ensemble method is that it can use unlabeled data to estimate the generalization error, while it still uses the entire labeled example set for training.

The cross-validation logarithmic opinion pool ensemble method is easily reformulated for another error function, as long as the error function has an ambiguity decomposition with target independent ambiguity. It is therefore possible to use the cross-validation ensemble method on all error functions in the deviance error family.

 

A language design development process is presented which leads to a language, gbeta, with a tight integration of virtual classes, general block structure, and a multiple inheritance mechanism based on coarse-grained structural type equivalence. From this emerges the concept of propagating specialization. The power lies in the fact that a simple expression can have far-reaching but well-organized consequences, e.g., in one step causing the combination of families of classes, then by propagation the members of those families, and finally by propagation the methods of the members. Moreover, classes are first class values which can be constructed at run-time, and it is possible to inherit from classes whether or not they are compile-time constants, and whether or not they were created dynamically. It is also possible to change the class and structure of an existing object at run-time, preserving object identity. Even though such dynamism is normally not seen in statically type-checked languages, these constructs have been integrated without compromising the static type safety of the language.

 

This booklet contains the proceedings of the Workshop on Software Engineering and Petri Nets (SEPN), held on June 26, 2000. The workshop was held in conjunction with the 21st International Conference on Application and Theory of Petri Nets (ICATPN-2000), organised by the CPN group of the Department of Computer Science, University of Aarhus, Denmark. The SEPN workshop papers are available in electronic form via the web page:
http://www.daimi.au.dk/pn2000/proceedings

 

This booklet contains the proceedings of the Workshop on Practical Use of High-level Petri Nets, June 27, 2000. The workshop is part of the 21st International Conference on Application and Theory of Petri Nets organised by the CPN group at the Department of Computer Science, University of Aarhus, Denmark. The workshop papers are available in electronic form via the web pages:
http://www.daimi.au.dk/pn2000/proceedings

 

An increasing number of system development projects are concerned with distributed and concurrent systems. There are numerous examples, ranging from large scale systems, in the areas of telecommunication and applications based on WWW technology, to medium or small scale systems, in the area of embedded systems. A typical distributed or concurrent system consists of a number of independent but communicating processes. This means that the execution of such systems may proceed in many different ways, e.g., depending on whether messages are lost, the speed of the processes involved, and the time at which input is received from the environment. As a result, distributed and concurrent systems are, by nature, complex and difficult to design and test. This has motivated the development of methods which support computer-aided analysis, validation, and verification of the behaviour of concurrent and distributed systems.
State space methods are some of the most prominent approaches in this field. The basic idea underlying state spaces is (in its simplest form) to compute all reachable states and state changes of the system, and represent these as a directed graph. The virtue of a constructed state space is that it makes it possible to algorithmically reason about the behaviour of a system, e.g., verify that the system possesses certain desired properties or locate errors in the system. The main disadvantage of using state spaces is the state explosion problem: even relatively small descriptions/systems may have an astronomically or even infinite number of reachable states, and it is a serious limitation on the use of state space methods in the analysis of real-life systems. The development of reduction methods to alleviate this inherent complexity problem is, therefore, a central topic in the development of state space methods. Reduction methods avoid representing the entire state space of the system or represent the state space in a compact form. The reduction is done in such a way that properties of the system can still be derived from the reduced state space.
In this thesis we study state space methods in the framework of Coloured Petri Nets which is a graphical language for modelling and analysis of concurrent and distributed systems. The thesis consists of two parts. Part I is the mandatory overview paper which summarises the work which has been done. Part II is composed of five individual papers and constitutes the core of this thesis. Four of the these papers have been published elsewhere as conference papers, journal papers, or book chapters.
The overview paper introduces the research field of state space methods for Coloured Petri Nets and summarises the contents and contributions of the five individual papers. A substantial part of the overview paper has also been devoted to putting the results presented in the five individual papers in a broader perspective in the form of a discussion of related work.
The first paper considers state space analysis of Coloured Petri Nets. It is well-known that almost all dynamic properties of the considered system can be verified when the state space is finite. However, state space analysis is more than just formulating a set of formal requirements and invoking a corresponding set of queries. State space analysis is also applicable during the design and debugging of a system. An approach towards this is to allow the user to analyse the behaviour of systems by drawing and generating selected parts of the state space. The paper presents a tool in which formal verification, partial state spaces, and analysis by means of graphical feedback and simulation are integrated entities. The focus of the paper is twofold: the support for graphical feedback and the way it has been integrated with simulation, and the underlying algorithms and datastructures which support computation and storage of state spaces and which exploit the hierarchical structure of the models.
The second paper presents a computer tool for verification of distributed systems. The tool implements the method of state spaces with symmetries. The basic idea in the approach is to exploit the symmetries inherent in many distributed systems in order to construct a condensed state space. As an example, the correctness of Lamport's Fast Mutual Exclusion Algorithm is established. We demonstrate a significant increase in the number of states which can be analysed. State spaces with symmetries is not our invention. Our contribution is the development of the tool and verification of the example, demonstrating how the method of state spaces with symmetries can be put into practical use.
The third paper demonstrates the potential of verification based on state spaces reduced by equivalence relations. The basic observation is that quite often some states of a system are similar, i.e., they induce similar behaviours. Similarity can be formally expressed by defining an equivalence relation on the set of states and on the set of actions of a system under consideration. A state space can be constructed in which the nodes correspond to equivalence classes of states, and the arcs correspond to equivalence classes of actions. Such a state space is often much smaller than the ordinary, full state space, but it does allow derivation of many verification results. State spaces with equivalence classes is not our invention. The contribution of the paper is the specification of a concrete notion of equivalence, and a demonstration of its application for verification of a communication protocol. Aided by a developed computer tool significant reductions of state spaces are exhibited, representing some first results on the practical use of state spaces with equivalence classes for Coloured Petri Nets. Exploiting the symmetries in systems induce a certain kind of equivalence. The verification of the communication protocol demonstrates the potential provided by more general notions of equivalence.
The fourth paper addresses the issue of using the stubborn set method for Coloured Petri Nets without relying on unfolding to the equivalent Place/Transition Net. The stubborn set method exploits the independence between actions to avoid representing all possible interleavings of the system execution. We give a lower bound result which states that there exist Coloured Petri Nets for which computing good stubborn sets requires time proportional to the size of the equivalent Place/Transition Net. We suggest an approximative method for computing stubborn sets of so-called process-partitioned Coloured Petri Nets which does not rely on unfolding. The underlying idea is to add some structure to the Coloured Petri Net, which can be exploited during the stubborn set construction to avoid the unfolding. The practical applicability of the method is demonstrated with both theoretical and experimental case studies, in which reduction of the state space, as well as savings in time, are obtained.
The fifth paper presents two new question-guided stubborn set methods for state properties. The first method makes it possible to determine whether a state is reachable in which a given state property holds. It generalises earlier results on stubborn sets for state properties in the sense that the earlier methods can be seen as an implementation of our more general method. We also propose alternative, more powerful implementations that have the potential of leading to better reduction results. This potential is demonstrated on some practical case studies. As an extension of the first method, we present a novel method which can be used to determine if it is always possible to reach a state where a given state property holds. Compared to earlier methods the benefit is again in the potential for better reduction results. omputer-aided analysis, validation, and verification of the behaviour of concurrent and distributed systems.

 

This paper advocates a ``bottom-up'' philosophy for the design of emotional systems for autonomous agents that is guided by functional concerns, and considers the particular case of designing emotions as mechanisms for action selection. The concrete realization of these ideas implies that the design process must start with an analysis of the requirements that the features of the environment, the characteristics of the action-selection task, and the agent architecture impose on the emotional system. This is particularly important if we see emotions as mechanisms that aim at modifying or maintaining the relation of the agent with its (external and internal) environment (rather than modifying the environment itself) in order to preserve the agent's goals. Emotions can then be selected and designed according to the roles they play with respect to this relation.

 

We report work on a LEGO robot capable of displaying several emotional expressions in response to physical contact. Our motivation has been to explore believable emotional exchanges to achieve plausible interaction with a simple robot. We have worked toward this goal in two ways.

First, acknowledging the importance of physical manipulation in children's interactions, interaction with the robot is through tactile stimulation; the various kinds of stimulation that can elicit the robot's emotions are grounded in a model of emotion activation based on different stimulation patterns.

Second, emotional states need to be clearly conveyed. We have drawn inspiration from theories of human basic emotions with associated universal facial expressions, which we have implemented in a caricaturized face. We have conducted experiments on both children and adults to assess the recognizability of these expressions.

 

We present two new question-guided stubborn set methods for state properties. The first method makes it possible to determine whether a marking is reachable in which a given state property holds. It generalises the results on stubborn sets for state properties recently suggested by Schmidt in the sense that that stubborn set method can be seen as an implementation of our more general method. We propose also alternative, more powerful implementations that have the potential of leading to better reduction results. This potential is demonstrated on some practical case studies.

As an extension of the first method, we present a second method which makes it possible to determine if from all reachable markings it is possible to reach a marking where a given state property holds. The novelty of this method is that it does not rely on ensuring that no transition is ignored in the reduced state space. Again, the benefit is in the potential for better reduction results.

 

This booklet contains the student reports from the course: Topics of Evolutionary Computation, Fall 2001, given by Thiemo Krink, Rene Thomsen and Rasmus K. Ursem

 

We here present a description of the system named Smart MIDI Interface (SMI), which converts analog and digital signals into MIDI messages and let an easy MIDI control over any kind of on/off actuator.
After examining some SMI applications, the paper gives an overview of the interface working principles, explaining the kind of data processing on analog and digital channels.
A detailed description of the engineered prototype is then considered, focusing attention on the various I/O connectors, the implemented MIDI messages and the other technical aspects interesting for the final user.