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https://hdl.handle.net/10784/28716

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Declarative debugging of functional logic programs
(Elsevier BV, 2001-01-01) Alpuente, M.; Correa, F.J.; Falaschi, M.; Universidad EAFIT. Departamento de Ciencias; Lógica y Computación
We present a general framework for the declarative debugging of functional logic programs, which is valid both for eager as well as lazy programs. We associate to our programs a semantics based on a (continuous) immediate consequence operator which models computed answers. Then we show that, given the intended specification of a program P, it is possible to check the correctness of P by a single step of the immediate consequence operator. We also present a more effective methodology which is based on abstract interpretation. By approximating the intended specification of the success set we derive a finitely terminating debugging method, which can be used statically. Our framework is parametric w.r.t. to the chosen approximation of the success set. We present one specific example of approximation. We provide an implementation of our debugging system which shows experimentally on a wide set of benchmarks that we are able to find some common errors in the user programs. © 2001 Published by Elsevier Science B. V.
A debugging scheme for functional logic programs
(Elsevier BV, 2002-01-01) Alpuente, M.; Correa, F.; Falaschi, M.; Universidad EAFIT. Departamento de Ciencias; Lógica y Computación
We present a generic scheme for the declarative debugging of functional logic programs which is valid for eager as well as lazy programs. In particular we show that the framework extends naturally some previous work and applies to the most modern lazy strategies, such as needed narrowing. First we associate to our programs a semantics based on a (continuous) immediate consequence operator, TR, which models computed answers. We show that, given the intended specification of a program R, it is possible to check the correctness of R by a single step of TR. We consider then a more effective methodology which is based on abstract interpretation: by approximating the intended specification of the success set we derive a finitely terminating diagnosis method, which can be used statically and is parametric w.r.t. to the chosen approximation. In order to correct the bugs, we sketch a preliminary deductive approach which uses example-guided unfolding. We specialize the incorrect rules w.r.t. sets of positive and negative examples which are gathered (bottom-up) during the diagnosis process, so that all refutations of negative examples and no refutation of positive examples are excluded. Our debugging framework does not require the user to either provide error symptoms in advance or answer difficult questions concerning program correctness. We extend an implementation of our system to the case of needed narrowing and illustrate it through some examples which demonstrate the practicality of our approach. © 2002 Published by Elsevier Science B.V.
Observations about an approximate algorithm for the point robot motion planning problem
(IEEE Computer Society, 2002-01-01) Trefftz, C.; Trefftz, H.; Universidad EAFIT. Departamento de Ingeniería de Sistemas; I+D+I en Tecnologías de la Información y las Comunicaciones
Observations about an approximate parallel algorithm for the point robot motion planning problem are presented. The algorithm solves not only the original problem, but related problems as well. © 2002 IEEE.
Achieving object persistence in an augmented reality indoor environment
(2003-01-01) Gutiérrez, M.D.; Márquez, A.M.; Trefftz, H.; Universidad EAFIT. Departamento de Ingeniería de Sistemas; I+D+I en Tecnologías de la Información y las Comunicaciones
In this paper we present a system for achieving object persistence in Augmented Reality Indoors Environments. In AR systems based on the Augmented Reality toolkit without object persistence, virtual objects appear and disappear as the corresponding pattern gets in and out of the user's field of view. Object persistence allows the environment to remember the relative position and orientation of virtual objects, making them appear more stable to the user. We describe object persistence as a series of transformations applied to the objects in a simple indoor environment. We then present the results of a quantitative experiment that shows how interactivity is improved by the use of object persistency.
Dynamic server allocation in virtual environments, using quadtrees for dynamic space partition
(2003-01-01) Restrepo, A.; Montoya, A.; Trefftz, H.; Universidad EAFIT. Departamento de Ingeniería de Sistemas; I+D+I en Tecnologías de la Información y las Comunicaciones
In actual applications of virtual environments, one of the problems that has received attention is the way to assign computational resources to those who participate in the system. In most cases, static resource allocation is used. Static allocation is simple but has several limitations, among them, the missutilization of resources. In this paper we present a proof-of-concept of a new system and report the results of experiments with a system that accomplishes dynamic resource allocation by using Quadtrees for space partitioning, in a Shared Virtual Environment.
Agents as tutors in augmented reality
(2003-01-01) Álvarez, N.; Trefftz, H.; Universidad EAFIT. Departamento de Ingeniería de Sistemas; I+D+I en Tecnologías de la Información y las Comunicaciones
Interaction between virtual entities and human beings should be similar to the normal interaction between human beings. Verbal interaction is the usual way of interaction among humans, but the interfaces that allow verbal communication between a human being and an agent (virtual human) have a limited vocabulary, need a lot of training and are expensive. In this paper we propose an Augmented Reality System with an unidirectional interface between an agent and a person. By using gestures, animations and adequate texts the agent can show a user how to perform a simple task. We hope that the tests to be conducted will show how useful this unidirectional interface is.
Handling heterogeneity in networked virtual environments
(MIT PRESS, 2003-02-01) Trefftz, H; Marsic, I; Zyda, M; Universidad EAFIT. Departamento de Ingeniería de Sistemas; I+D+I en Tecnologías de la Información y las Comunicaciones
The availability of inexpensive and powerful graphics cards as well as fast Internet connections make networked virtual environments viable for millions of users and many new applications. It is therefore necessary to cope with the growing heterogeneity that arises from differences in computing power, network speed, and users' preferences. This paper describes an architecture that accommodates the heterogeneity while allowing a manager to define systemwide policies. One of the main objectives of our scheme is to allow slower nodes to participate in the session by preventing fast nodes from flooding slow nodes with too many messages. Policies and users' preferences can be expressed as simple linear equations forming a model that describes the system as a whole as well as its individual components. When solutions to this model are mapped back to the problem domain, viable solutions that accommodate heterogeneity and system policies are obtained. For example, slower nodes may receive less frequent updates than faster ones for one or several information streams. The results of our experiments with a proof-of-concept system are described.
Combinatory multicast for differentiated data transmission in distributed virtual environments
(ACTA PRESS, 2004-01-01) Quiroz, A; Trefftz, H; Universidad EAFIT. Departamento de Ingeniería de Sistemas; I+D+I en Tecnologías de la Información y las Comunicaciones
The shortage of multicast addresses is a factor that limits their use in Intemet-based applications. Since multicast plays a very important role in supporting resource heterogeneity among users of applications with a high demand of computational resources, such as Distributed Virtual Environments, the sparing use of these addresses is of great importance. This paper suggests a scheme for the combination of multicast groups for differentiated data transmission, based on layered multicast, with which the number of different levels of service that can be provided to users of a shared virtual environment with a fixed number of groups is multiplied. For applications where the levels of service correspond to different transmission rates, the scheme also significantly reduces bandwidth utilization. We present a basic method for its implementation and describe preliminary tests to prove its functionality.
A collaborative tool for synchronous distance education
(2004-01-01) Agudelo, A.; Escobar, L.; Restrepo, J.; Quiroz, A.; Trefftz, H.; Universidad EAFIT. Departamento de Ingeniería de Sistemas; I+D+I en Tecnologías de la Información y las Comunicaciones
In this paper we report results of the use of a telepresence application in a simulated distance education setting. The application combines video-conference with a networked virtual environment in which the instructor and the students can experiment with virtual object in a collaborative manner. The teaching for Understanding (TFU) framework is used as the pedagogical approach. Current preliminary results show that the combination of the telepresence application with TFU, can compensate for the lack of physical presence of the instructor in the classroom.
Numerical simulations of a possible hypercomputational quantum algorithm
(SPRINGER-VERLAG WIEN, 2005-01-01) Sicard, A; Ospina, J; Velez, M; Universidad EAFIT. Departamento de Ciencias; Lógica y Computación
The hypercomputers compute functions or numbers, or more generally solve problems or carry out tasks, that cannot be computed or solved by a Turing machine. Several numerical simulations of a possible hypercomputational algorithm based on quantum computations previously constructed by the authors are presented. The hypercomputability of our algorithm is based on the fact that this algorithm could solve a classically non-computable decision problem, the Hilbert's tenth problem. The numerical simulations were realized for three types of Diophantine equations: with and without solutions in non-negative integers, and without solutions by way of various traditional mathematical packages.
BDNG: A dublin core-based architecture for digital libraries
(2005-01-01) Montoya, E.; Ruiz, M.; Giraldo, J.; Universidad EAFIT. Departamento de Ingeniería de Sistemas; I+D+I en Tecnologías de la Información y las Comunicaciones
Digital Libraries will be one of the main ways to access structured information through the Internet. Information related to resources or objects is known as metadata. Several metadata models have been proposed; however, the model proposed by the Dublin Core Metadata Initiative (DCMI) [1] has demonstrated great utility in digital libraries. The simplicity and generality of DCMI has facilitated the deployment of digital libraries and their interoperability. This paper proposes DCMI as metadata model in our own Digital Library Architecture (Biblioteca Digital de Nueva Generación -BDNG). We have extended DCMI and used some elements of DC-Library application profile (DC-Lib) [2] in addition to new elements not previously considered. This paper presents the metadata models for the following applications: digital library of EAFIT University (BDEeafit), integration of digital or referential libraries (BDMetaLib) and digital library for E-Learning systems (BDEI). This paper also describes the general architecture of BDNG.
A possible hypercomputational quantum algorithm
(SPIE-INT SOC OPTICAL ENGINEERING, 2005-01-01) Sicard, A; Velez, M; Ospina, J; Universidad EAFIT. Departamento de Ciencias; Lógica y Computación
The term `hypermachine' denotes any data processing device (theoretical or that can be implemented) capable of carrying out tasks that cannot be performed by a Turing machine. We present a possible quantum algorithm for a classically non-computable decision problem, Hilbert's tenth problem; more specifically, we present a possible hypercomputation model based on quantum computation. Our algorithm is inspired by the one proposed by Tien D. Kieu, but we have selected the infinite square well instead of the (one-dimensional) simple harmonic oscillator as the underlying physical system. Our model exploits the quantum adiabatic process and the characteristics of the representation of the dynamical Lie algebra su(1, 1) associated to the infinite square well.
Basic reproductive rate of a spatial epidemic model using computer algebra software
(2005-01-01) Doracelly Hincapié, P.; Juan Ospina, G.; Universidad EAFIT. Departamento de Ciencias; Lógica y Computación
Using computer algebra software we obtain the basic reproductive rate corresponding to the propagation of a directly transmitted disease in a circular habitat when the disease is endemic at the boundary. The method used is the Laplace Transform Technique and calculus of residues. The results that were obtained include both the explicit form of the R0 for the boundary condition that was considered, as the explicit symbolic solution of the model equation. The method that was used can be extended to other more complex problems such as indirectly transmitted diseases with one or more intermediary hosts or effects of genetic, immunological, geographical or social heterogeneity in the human population. This application indicates that the computer algebra software for symbolic computation has a very promissory future in mathematical epidemiology.
Mackendrick: A Maple Package oriented to symbolic computational epidemiology
(SPRINGER, 2006-01-01) Ospina, Juan; Hincapie, Doracelly; Universidad EAFIT. Departamento de Ciencias; Lógica y Computación
A Maple Package named Mackendrick is presented. Such package is oriented to symbolic computational epidemiology. © Springer-Verlag Berlin Heidelberg 2006.
Collaborative and distributed augmented reality in teaching multi-variate calculus
(2006-01-01) Orozco, C.; Esteban, P.; Trefftz, H.; Universidad EAFIT. Departamento de Ingeniería de Sistemas; I+D+I en Tecnologías de la Información y las Comunicaciones
This article presents the first results of using an Augmented Reality (AR) tool, designed to support tutoring sessions in multi-variate calculus. The tool is used either in a face-to-face setting in which the instructor and the students are collocated or in a distance setting, in which the instructor and students are physically in remote places. The tool was used with two groups of students of Differential Calculus. The students had not been exposed to the concept of equations involving 3 variables and the corresponding surfaces in space. The experience explored how students generalized 2D graphics and equations with their 3D surfaces counterparts with the help of the tool.
Using computer algebra for Yang-Baxterization applied to quantum computing
(SPIE-INT SOC OPTICAL ENGINEERING, 2006-05-12) Velez, Mario; Ospina, Juan; Universidad EAFIT. Departamento de Ciencias; Lógica y Computación
Using Computer Algebra Software (Mathematica and Maple), the recently introduced topic of Yang-Baxterization applied to quantum computing, is explored from the mathematical and computational views. Some algorithms of computer algebra were elaborated with the aim to make the calculations to obtain some of results that were originally presented in the paper by Shang-Kauffman-Ge. Also certain new results about computational Yang-baxterization are presented. We obtain some Hamiltonians for hypothetical physical systems which can be realized within the domain of spin chains and certain diffusion process. We conclude that it is possible to have real physical systems on which implement, via Yang-baxterization, the standard quantum gates with topological protection. Finally some lines for future research are deligned.
Spatial epidemic patterns recognition using computer algebra
(SPRINGER, 2007-01-01) Hincapié, D.; Ospina, J.; Universidad EAFIT. Departamento de Ciencias; Lógica y Computación
An exploration in Symbolic Computational bio-surveillance is showed. The main obtained results are that the geometry of the habitat determines the critical parameters via the zeroes of the Bessel functions and the explicit forms of the static and non-static spatial epidemic patterns. © Springer-Verlag Berlin Heidelberg 2007.
Collaborative virtual environments for teaching physics
(SPRINGER, 2007-01-01) Giraldo, F.; Rojas, Á.M.J.; Esteban, P.; Trefftz, H.; Universidad EAFIT. Departamento de Ingeniería de Sistemas; I+D+I en Tecnologías de la Información y las Comunicaciones
Eafit University created a Telepresence application for distance education. It supports bidirectional audio and video and a shared virtual environment that allows the instructor and students to manipulate virtual objects in a collaborative manner, thereby reinforcing the learning process. In this paper we report the experience of creating new contents and deploying the tool in a Physics course at Universidad del Quindío. The tool was improved an extended in order to include new functionality and make it easier for development teams to create new content. Teaching for Understanding was used as pedagogical framework for course creation and also as a guide to develop the interviews that were used to capture user's perceptions and to asses the improvements in the learning process. The results showed that the use of the tool had a positive impact on the students' understanding of the topics at hand. © 2007 Springer.
Universal quantum gates Via Yang-baxterization of dihedral quantum double
(SPRINGER, 2007-01-01) Velez, Mario; Ospina, Juan; Universidad EAFIT. Departamento de Ciencias; Lógica y Computación
The recently discovered Yang-Baxterization process for the quantum double of the dihedral group algebra, is presented keeping on mind the quantum computation. The products resultant from Yang-Baxterization process are interpreted as universal quantum gates using the Bryslinski's theorem. Results are obtained for two-qubits and two-qutrits gates. Using the Zhang-Kauffman-Ge method (ZKGM), certain Hamiltonians responsible for the quantum evolution of the quantum gates are obtained. Possible physical systems such as anyons systems are mentioned as referents for practical implementation. © Springer-Verlag Berlin Heidelberg 2007.
Analytical solution for transient flow of a generalized bingham fluid with memory in a movable tube using computer algebra
(SPRINGER, 2007-01-01) Ospina, Juan; Velez, Mario; Universidad EAFIT. Departamento de Ciencias; Lógica y Computación
A rheological linear model for a certain generalized Bingham fluid with rheological memory, which flows in a movable tube is proposed and analytically solved. The model is a system of two linear and coupled partial differential equations with integral memory. We apply the Laplace transform method making the inverse transform by means of the Bromwich integral and the theorem of residues and the analytical solution are obtained using computer algebra. We deduce the explicit forms of the velocity and stress profiles for the generalized Bingham fluid in terms of Bessel and Struve functions. Various limit cases are obtained and the standard Hagen-Poiseuille and Buckingham-Reiner equations are recovered from more general equations. This works shows the powerful of Maple to solve complex rheological problems in an analytical form as it is presented here by the first time. © Springer-Verlag Berlin Heidelberg 2007.

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