23,141 research outputs found
Towards declarative diagnosis of constraint programs over finite domains
The paper proposes a theoretical approach of the debugging of constraint
programs based on a notion of explanation tree. The proposed approach is an
attempt to adapt algorithmic debugging to constraint programming. In this
theoretical framework for domain reduction, explanations are proof trees
explaining value removals. These proof trees are defined by inductive
definitions which express the removals of values as consequences of other value
removals. Explanations may be considered as the essence of constraint
programming. They are a declarative view of the computation trace. The
diagnosis consists in locating an error in an explanation rooted by a symptom.Comment: In M. Ronsse, K. De Bosschere (eds), proceedings of the Fifth
International Workshop on Automated Debugging (AADEBUG 2003), September 2003,
Ghent. cs.SE/030902
A reusable iterative optimization software library to solve combinatorial problems with approximate reasoning
Real world combinatorial optimization problems such as scheduling are
typically too complex to solve with exact methods. Additionally, the problems
often have to observe vaguely specified constraints of different importance,
the available data may be uncertain, and compromises between antagonistic
criteria may be necessary. We present a combination of approximate reasoning
based constraints and iterative optimization based heuristics that help to
model and solve such problems in a framework of C++ software libraries called
StarFLIP++. While initially developed to schedule continuous caster units in
steel plants, we present in this paper results from reusing the library
components in a shift scheduling system for the workforce of an industrial
production plant.Comment: 33 pages, 9 figures; for a project overview see
http://www.dbai.tuwien.ac.at/proj/StarFLIP
Formal verification of AI software
The application of formal verification techniques to Artificial Intelligence (AI) software, particularly expert systems, is investigated. Constraint satisfaction and model inversion are identified as two formal specification paradigms for different classes of expert systems. A formal definition of consistency is developed, and the notion of approximate semantics is introduced. Examples are given of how these ideas can be applied in both declarative and imperative forms
The KB paradigm and its application to interactive configuration
The knowledge base paradigm aims to express domain knowledge in a rich formal
language, and to use this domain knowledge as a knowledge base to solve various
problems and tasks that arise in the domain by applying multiple forms of
inference. As such, the paradigm applies a strict separation of concerns
between information and problem solving. In this paper, we analyze the
principles and feasibility of the knowledge base paradigm in the context of an
important class of applications: interactive configuration problems. In
interactive configuration problems, a configuration of interrelated objects
under constraints is searched, where the system assists the user in reaching an
intended configuration. It is widely recognized in industry that good software
solutions for these problems are very difficult to develop. We investigate such
problems from the perspective of the KB paradigm. We show that multiple
functionalities in this domain can be achieved by applying different forms of
logical inferences on a formal specification of the configuration domain. We
report on a proof of concept of this approach in a real-life application with a
banking company. To appear in Theory and Practice of Logic Programming (TPLP).Comment: To appear in Theory and Practice of Logic Programming (TPLP
Constraint capture and maintenance in engineering design
The Designers' Workbench is a system, developed by the Advanced Knowledge Technologies (AKT) consortium to support designers in large organizations, such as Rolls-Royce, to ensure that the design is consistent with the specification for the particular design as well as with the company's design rule book(s). In the principal application discussed here, the evolving design is described against a jet engine ontology. Design rules are expressed as constraints over the domain ontology. Currently, to capture the constraint information, a domain expert (design engineer) has to work with a knowledge engineer to identify the constraints, and it is then the task of the knowledge engineer to encode these into the Workbench's knowledge base (KB). This is an error prone and time consuming task. It is highly desirable to relieve the knowledge engineer of this task, and so we have developed a system, ConEditor+ that enables domain experts themselves to capture and maintain these constraints. Further we hypothesize that in order to appropriately apply, maintain and reuse constraints, it is necessary to understand the underlying assumptions and context in which each constraint is applicable. We refer to them as “application conditions” and these form a part of the rationale associated with the constraint. We propose a methodology to capture the application conditions associated with a constraint and demonstrate that an explicit representation (machine interpretable format) of application conditions (rationales) together with the corresponding constraints and the domain ontology can be used by a machine to support maintenance of constraints. Support for the maintenance of constraints includes detecting inconsistencies, subsumption, redundancy, fusion between constraints and suggesting appropriate refinements. The proposed methodology provides immediate benefits to the designers and hence should encourage them to input the application conditions (rationales)
Anytime diagnosis for reconfiguration
Many domains require scalable algorithms that help to determine diagnoses efficiently
and often within predefined time limits. Anytime diagnosis is able to determine
solutions in such a way and thus is especially useful in real-time scenarios such as production
scheduling, robot control, and communication networks management where diagnosis
and corresponding reconfiguration capabilities play a major role. Anytime diagnosis in
many cases comes along with a trade-off between diagnosis quality and the efficiency of
diagnostic reasoning. In this paper we introduce and analyze FLEXDIAG which is an anytime
direct diagnosis approach. We evaluate the algorithm with regard to performance and diagnosis quality using a configuration benchmark from the domain of feature models and
an industrial configuration knowledge base from the automotive domain. Results show that
FLEXDIAG helps to significantly increase the performance of direct diagnosis search with
corresponding quality tradeoffs in terms of minimality and accuracy
Configuration Analysis for Large Scale Feature Models: Towards Speculative-Based Solutions
Los sistemas de alta variabilidad son sistemas de software en los que la gestión de la
variabilidad es una actividad central. Algunos ejemplos actuales de sistemas de alta
variabilidad son el sistema web de gesión de contenidos Drupal, el núcleo de Linux,
y las distribuciones Debian de Linux.
La configuración en sistemas de alta variabilidad es la selección de opciones
de configuración según sus restricciones de configuración y los requerimientos de
usuario. Los modelos de características son un estándar “de facto” para modelar las
funcionalidades comunes y variables de sistemas de alta variabilidad. No obstante,
el elevado número de componentes y configuraciones que un modelo de características
puede contener hacen que el análisis manual de estos modelos sea una tarea muy
costosa y propensa a errores. Así nace el análisis automatizado de modelos de características
con mecanismos y herramientas asistidas por computadora para extraer
información de estos modelos. Las soluciones tradicionales de análisis automatizado
de modelos de características siguen un enfoque de computación secuencial para
utilizar una unidad central de procesamiento y memoria. Estas soluciones son adecuadas
para trabajar con sistemas de baja escala. Sin embargo, dichas soluciones demandan
altos costos de computación para trabajar con sistemas de gran escala y alta
variabilidad. Aunque existan recusos informáticos para mejorar el rendimiento de
soluciones de computación, todas las soluciones con un enfoque de computación secuencial
necesitan ser adaptadas para el uso eficiente de estos recursos y optimizar su
rendimiento computacional. Ejemplos de estos recursos son la tecnología de múltiples
núcleos para computación paralela y la tecnología de red para computación distribuida.
Esta tesis explora la adaptación y escalabilidad de soluciones para el analisis automatizado
de modelos de características de gran escala. En primer lugar, nosotros
presentamos el uso de programación especulativa para la paralelización de soluciones.
Además, nosotros apreciamos un problema de configuración desde otra perspectiva,
para su solución mediante la adaptación y aplicación de una solución no
tradicional. Más tarde, nosotros validamos la escalabilidad y mejoras de rendimiento
computacional de estas soluciones para el análisis automatizado de modelos de características
de gran escala.
Concretamente, las principales contribuciones de esta tesis son:
• Programación especulativa para la detección de un conflicto mínimo y
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preferente. Los algoritmos de detección de conflictos mínimos determinan
el conjunto mínimo de restricciones en conflicto que son responsables de comportamiento
defectuoso en el modelo en análisis. Nosotros proponemos una
solución para, mediante programación especulativa, ejecutar en paralelo y reducir
el tiempo de ejecución de operaciones de alto costo computacional que
determinan el flujo de acción en la detección de conflicto mínimo y preferente
en modelos de características de gran escala.
• Programación especulativa para un diagnóstico mínimo y preferente. Los
algoritmos de diagnóstico mínimo determinan un conjunto mínimo de restricciones
que, por una adecuada adaptación de su estado, permiten conseguir un
modelo consistente o libre de conflictos. Este trabajo presenta una solución
para el diagnóstico mínimo y preferente en modelos de características de gran
escala mediante la ejecución especulativa y paralela de operaciones de alto
costo computacional que determinan el flujo de acción, y entonces disminuir
el tiempo de ejecución de la solución.
• Completar de forma mínima y preferente una configuración de modelo
por diagnóstico. Las soluciones para completar una configuración parcial
determinan un conjunto no necesariamente mínimo ni preferente de opciones
para obtener una completa configuración. Esta tesis soluciona el completar
de forma mínima y preferente una configuración de modelo mediante técnicas
previamente usadas en contexto de diagnóstico de modelos de características.
Esta tesis evalua que todas nuestras soluciones preservan los valores de salida esperados,
y también presentan mejoras de rendimiento en el análisis automatizado de
modelos de características con modelos de gran escala en las operaciones descrita
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