Efficient Path Consistency Algorithms for Constraint Satisfaction Problems

A large number of problems can be formulated as special cases of the Constraint Satisfaction Problem (CSP). In such a problem, the task specification can be formulated to consist of a set of variables, a domain for each variable and a set of constraints on these variables. A typical task is then to find an instantiation of these variables (to values in their respective domains) such that all the constraints are simultaneously satisfied. Most of the methods used to solve such problems are based on some backtracking scheme, which can be very inefficient with exponential run-time complexity for most nontrivial problems. Path consistency algorithms constitute an important class of algorithms used to simplify the search space, either before or during search, by eliminating inconsistent values from the domains of the corresponding variables. However, the use of these algorithms in real life applications has been limited, mainly, due to their high space complexity. Han and Lee [5] presented a path consistency algorithm, PC-4, with 0(n3a3) space complexity, which makes it practicable only for small problems. I present a new path consistency algorithm, PC-5, which has an 0(n3a2) space complexity while retaining the worst-case time complexity of PC-4. Moreover, the new algorithm exhibits a much better average-case time complexity. The new algorithm is based on the idea (due to Bessiere [1]) that, at any time, only a minimal amount of support has to be found and recorded for a labeling to establish its viability; one has to look for a new support only if the current support is eliminated. I also show that PC-5 can be improved further to yield an algorithm, PC5++, with even better average-case performance and the same space complexity. I present experimental results evaluating the performance of these algorithms on various classes of problems. The results show that both PC-5 and PC5++ significantly outperform PC-4, both in terms of space and time, with PC5++ being the better of the two algorithms presented

Propagating orientation constraints for the Hubble Space Telescope

An observing program on the Hubble Space Telescope (HST) is described in terms of exposures that are obtained by one or more of the instruments onboard the HST. Many requested exposures might specify orientation requirements and accompanying ranges. Orientation refers to the amount of roll (in degrees) about the line of sight. The range give the permissible tolerance (also in degrees). These requirements may be (1) absolute (in relation to the celestial coordinate system), (2) relative to the nominal roll angle for HST during that exposure, or (3) relative (in relation to other exposures in the observing program). The TRANSformation expert system converts proposals for astronomical observations with HST into detailed observing plans. Part of the conversion involves grouping exposures into higher level structures based on exposure characteristics. Exposures constrained to be at different orientations cannot be grouped together. Because relative orientation requirements cause implicit constraints, orientation constraints have to be propagated. TRANS must also identify any inconsistencies that may exist so they can be corrected. We have designed and implemented an orientation constraint propagator as part of TRANS. The propagator is based on an informal algebra that facilitates the setting up and propagation of the orientation constraints. The constraint propagator generates constraints between directly related exposures, and propagates derived constraints between exposures that are related indirectly. It provides facilities for path-consistency checking, identification of unsatisfiable constraints, and querying of orientation relationships. The system has been successfully operational as part of TRANS for over seven months. The solution has particular significance to space applications in which satellite/telescope pointing and attitude are constrained and relationships exist between multiple configurations

MUSE CSP: An Extension to the Constraint Satisfaction Problem

This paper describes an extension to the constraint satisfaction problem (CSP) called MUSE CSP (MUltiply SEgmented Constraint Satisfaction Problem). This extension is especially useful for those problems which segment into multiple sets of partially shared variables. Such problems arise naturally in signal processing applications including computer vision, speech processing, and handwriting recognition. For these applications, it is often difficult to segment the data in only one way given the low-level information utilized by the segmentation algorithms. MUSE CSP can be used to compactly represent several similar instances of the constraint satisfaction problem. If multiple instances of a CSP have some common variables which have the same domains and constraints, then they can be combined into a single instance of a MUSE CSP, reducing the work required to apply the constraints. We introduce the concepts of MUSE node consistency, MUSE arc consistency, and MUSE path consistency. We then demonstrate how MUSE CSP can be used to compactly represent lexically ambiguous sentences and the multiple sentence hypotheses that are often generated by speech recognition algorithms so that grammar constraints can be used to provide parses for all syntactically correct sentences. Algorithms for MUSE arc and path consistency are provided. Finally, we discuss how to create a MUSE CSP from a set of CSPs which are labeled to indicate when the same variable is shared by more than a single CSP.Comment: See http://www.jair.org/ for any accompanying file

Dimensions of a brunch experience: a study about the consumer behavior, the drivers, and the post-consumption phase of brunches in Lisbon

The world of restauration is full of different concepts and services, with the strategic objective of places to stand out and offer different experiences to consumers. Brunch is one of those concepts that, in the middle of the 21st century, is gaining a huge popularity among different types of consumers with different needs and standards. The main objective of this study is to understand and identify what is most valued during the Brunch experience, what are their drivers and what conclusions can be drawn based on the reviews shared in the post-consumer phase of the process. In addition, this dissertation also intends to understand if the dimensions of the experience vary according to the "gender" segment, from Brunch to Brunch and according to the evaluations given in the 734 comments online. The tools used to analyze the main themes of the comments were Wordle and Leximancer. After this process, the themes were displayed graphically on a conceptual map from which results data from 4 distinct Brunch restaurants: Nicolau Lisboa, Heim Café, Fauna & Flora and Zenith Brunch & Cocktail. From this analysis, 13 themes that depict the experience in a Brunch were discovered: Brunch space pancakes place waiting delicious time juice try people best recommend experience. It was also possible to conclude that there are several variables that impact the experience during brunch, that the reviews are a very useful tool to remove points to improve for the restaurant itself and that there is a gender divergence in what is valued at a brunch. In this dissertation it is revealed that the different ratings given in the Zomato platform represent different themes of the experience.O mundo da restauração está repleto de conceitos e serviços diferentes, com o objectivo estratégico dos espaços se destacarem e oferecerem experiências distintas aos consumidores. O Brunch é um desses conceitos que, em pleno século XXI, está a ganhar uma popularidade imensa junto de diferentes tipos de consumidor que apresentam necessidades e padrões distintos. O principal ojectivo deste estudo é entender e identificar o que é mais valorizado durante a experiência de Brunch, quais os seus drivers e que conclusões se podem retirar com base nas reviews partilhadas na fase pós-consumo do processo. Complementarmente, esta dissertação pretende também perceber se as dimensões da experiência variam de acordo com o segmento “genero”, de Brunch para Brunch e de acordo com as avaliações dadas nos 734 comentários online. As ferramentas utilizadas para a analise dos principais temas dos comentários são o Wordle e o Leximancer. Após esse processo, os temas são expostos graficamente num mapa conceptual do qual derivam resultados de 4 restaurantes de Brunch distintos: Nicolau Lisboa, Heim Café, Fauna & Flora e Zenith Brunch & Cocktail. Desta análise retiraramse 13 temas que retratam a experiência num Brunch: Brunch, espaço, panquecas, lugar, espera, delicioso, tempo, sumo, experimentar, pessoas, melhor, recomendação, experiencia. Foi também possivel concluir que existem várias variáveis que impactam a experiencia durante o brunch, que as reviews são uma ferramenta muito útil para retirar pontos a melhorar para o próprio restaurante e que existe uma divergência de genero no que toca ao que é valorizado num brunch. Nesta dissertação revela-se que os diferentes ratings dados na plataforma Zomato representam diferentes temas da experiência

A framework for cause-related marketing campaigns with customer choice in a collectivistic cultural context

This research is an exploration of how customer engagement, through the possibility of choosing the structural elements of a Cause-Related Marketing (CRM) campaign, could influence a) CRM success, in terms of coverage, customization and reduced consumer skepticism and b) to cultivate positive Word-of-Mouth (WOM) persuasion behavior. A conceptual framework is developed which comprises three main components. These are (1) choice of cause, (2) choice of cause proximity and (3) choice of donation type. The empirical stage of the study applied a case study methodology and was developed through a cross-sectional study of twenty key informants, Cypriot customers of the retail banking industry in Cyprus. The qualitative data collected through semi-structured interviews and were compared and contrasted with the initial conceptual framework and the relevant literature. The emergent patterns within this analysis showed that both three components of the framework positively affected CRM success in terms of coverage, customization, reduced skepticism and positive WOM persuasion behavior. However, the results also showed that in some cases, choice of cause type and choice of cause proximity could create feelings of guilt to the customers, and the solution in avoiding such feelings was to provide the customers with the ability to choose multiple cause types or to change their cause proximity choice over time. Also, in terms of the underlying mechanisms that trigger consumers to choose the various structural elements of the CRM campaign, the results showed evidence of the existence of fit between the cause type and the donation type, a type of fit that its introduced for the first time in the CRM literature. Finally, this study 1) links, for the first time, procedural justice theory with reduced consumer skepticism and perceived transparency for the CRM campaign and 2) uncovers various consumers' attitudes as regards to the type of donation. In conclusion, this dissertation discusses the contributions to the CRM field and the implications for both academics and practitioners

Una contribución a la programación cognitiva: arquitecturas de segunda generación para representación del conocimiento

La tesis propone el concepto y diseño de una arquitectura cognitiva para representación de conocimiento profesional especializado en clases de dominios relacionados con el mundo físico. Constituye una extensión de los trabajos de B.Chandrasekaran, potenciando el concepto de arquitectura basada en tareas genéricas propuesta por dicho autor. En base a la arquitectura propuesta, se ha desarrollado un entorno como herramienta de construcción de sistemas expertos de segunda generación, así como un lenguaje para programación cognitiva (DECON)- Dicho entorno, programado en lenguaje C sobre UNIX, ha sido utilizado para el desarrollo de un sistema para predicción de avenidas en la Cuenca Hidrográfica del Jucar, en el marco del proyecto SAIH. Primeramente, la tesis plantea el problema de la modelización del comportamiento de los sistemas físicos, reflejando las limitaciones de las formas clásicas de representación del conocimiento para abordar dicho problema, así como los principales enfoques más recientes basados en el concepto de arquitectura cognitiva y en las técnicas de simulación cualitativa. Se realiza después una síntesis de la arquitectura propuesta, a nivel del conocimiento, para detallar posteriormente su desarrollo a nivel simbólico y de implementación, así como el método general para la construcción de modelos sobre la arquitectura. Se muestra también un resumen de los principales aspectos del desarrollo de software. Finalmente, en forma de anejos, se presenta un caso de estudio, el sistema SIRAH (Sistema Inteligente de Razonamiento Hidrológico), junto con la gramática formal del lenguaje de soporte para la definición de modelos.---ABSTRACT---The thesis proposes the concept and design of a cognitive architecture for professional knowledge representation, specialized in domain classes related to the physical world. It is an extensión of the Chandrasekaran's work, improving the concept of Generic Task based architecture introduced by this author. Based on the proposed architecture, an environment has been developed, as a case of second generation building expert systems tool, as well as a language for cognitive programming (DECON). The environment, programmed in C lenguage on UNIX operating system, has been used to develop a system for flood prediction in the Jucar watershed, inside of the SAIH project. Firstly, the behavior modeling problem of physical systems is discussed, showing the limitations of the classical representations to tackle it, beside the most recent approaches based on cognitive architecture concepts and qualitative simulation technique. An overview of the architecture at the knowledge level is then made, being followed by its symbolic and implementation level description, as well as a general guideline for building models on top of the architecture. The main aspects of software development are also introduced. Finaly, as annexes, a case of study -the SIRAH system (Sistema Inteligente de RAzonamiento Hidrológico)- is introduced, along with the formal grammar of the support language for model definition