Pseudo-contractions as Gentle Repairs

Updating a knowledge base to remove an unwanted consequence is a challenging task. Some of the original sentences must be either deleted or weakened in such a way that the sentence to be removed is no longer entailed by the resulting set. On the other hand, it is desirable that the existing knowledge be preserved as much as possible, minimising the loss of information. Several approaches to this problem can be found in the literature. In particular, when the knowledge is represented by an ontology, two different families of frameworks have been developed in the literature in the past decades with numerous ideas in common but with little interaction between the communities: applications of AGM-like Belief Change and justification-based Ontology Repair. In this paper, we investigate the relationship between pseudo-contraction operations and gentle repairs. Both aim to avoid the complete deletion of sentences when replacing them with weaker versions is enough to prevent the entailment of the unwanted formula. We show the correspondence between concepts on both sides and investigate under which conditions they are equivalent. Furthermore, we propose a unified notation for the two approaches, which might contribute to the integration of the two areas

Vacina contra HPV como prevenção de câncer de colo de útero

O câncer de colo de útero é uma realidade entre mulheres de todo o mundo. Objetivou-se neste estudo avaliar a importância da imunização ativa, por meio da vacinação contra o Papiloma Vírus Humano (HPV), na diminuição da incidência de casos de neoplasias de colo uterinas. Este estudo trata-se de uma mini revisão de literatura de artigos recentes (produzidos nos últimos 5 anos), na qual a coleta de dados deu-se a partir do Portal Regional da Biblioteca Virtual em Saúde, utilizando os descritores da área da saúde do Portal DeCS/MeSH, “Vacina Quadrivalente Recombinante contra HPV tipos 6, 11, 16, 18” e “Neoplasias do Colo do Útero”, além do operador booleano “AND”. O estudo apresenta que os imunizantes contra o Papiloma Vírus Humano são eficazes em suas propostas e quanto mais cedo são aplicados nos pacientes mais surtem um efeito consistente, alguns em maiores e outros em menor grau, levando em conta seu custo e sua eficácia. Os principais imunizantes citados no estudo são HPV Quadrivalente e a vacina HPV Nonavalente que possuem uma eficácia parecida, com diferença de 10,46% entre as duas. Dessa forma, o estudo desenhou-se mostrando que a HPV Quadrivalente, apesar de possuir menor eficácia, torna-se a mais viável em função de seu maior custo- benefício. Assim, conclui-se que a vacinação é uma grande ferramenta na diminuição da incidência de câncer de colo de útero, devendo ser expandida entre todas as camadas sociais, sobretudo nas de menor poder aquisitivo, as quais concentram grande parte dos números de casos de neoplasias

Operações de pseudocontração para lógicas de descrição

Knowledge representation in ontologies is based on Description Logics, which are decidable fragments of first-order logic. Since knowledge is not static, it is necessary to deal with the acquisition of new information, which may contradict the existing knowledge. Belief Revision aims to solve this problem, but the classical AGM framework assumes an ideal agent that is able to deal with logically closed sets of sentences, and some of its generalisations for belief bases (such as ontologies represented in Description Logics) may lead to loss of information due to the fact that no sentence can be added when a contraction operation is performed. In this work, we analyse kernel constructions for pseudo-contraction operations and their formal properties. Also, we show the close relationship between concepts and definitions of Belief Revision and Ontology Repair (such as pseudo-contractions and gentle repairs, respectively), and we propose a unified notation for their operations.A representação de conhecimento em ontologias é baseada em Lógicas de Descrição, que são fragmentos decidíveis da lógica de primeira ordem. Uma vez que o conhecimento não é estático, é necessário lidar com a aquisição de novas informações, que podem contradizer o conhecimento existente. Revisão de Crenças busca resolver este problema, mas o arcabouço clássico AGM supõe um agente ideal capaz de lidar com conjuntos de sentenças fechados logicamente, e algumas de suas generalizações para bases de crenças (como ontologias representadas com Lógicas de Descrição) podem levar a uma perda de informação, visto que nenhuma sentença pode ser adicionada ao realizar uma operação de contração. Neste trabalho, analisamos construções kernel para operações de pseudocontração e suas propriedades formais. Ademais, mostramos a relação próxima que existe entre os conceitos e definições das áreas de Revisão de Crenças e Reparo de Ontologias (tais como pseudocontrações e reparos brandos, respectivamente), e apresentamos uma notação unificada para suas operações

Partial meet pseudo-contractions

In the AGM paradigm for belief revision, epistemic states are represented by logically closed sets of sentences, the so-called belief sets. An alternative approach uses belief bases, arbitrary sets of sentences. Both approaches have their problems when it comes to contraction operations. Belief bases are more expressive, but, at the same time, they present a serious syntax dependence. Between those two extremes lie a whole gamut of operations called pseudo-contractions, some of which may be interesting alternatives to the classical ones, providing a good balance between syntax dependence and expressivity. In this paper we explore some very natural and general constructions for pseudo-contractions, showing some of their properties and giving their axiomatic characterizations. We also illustrate possible practical scenarios where they can be employed

Pseudo-contractions as Gentle Repairs

Updating a knowledge base to remove an unwanted consequence is a challenging task. Some of the original sentences must be either deleted or weakened in such a way that the sentence to be removed is no longer entailed by the resulting set. On the other hand, it is desirable that the existing knowledge be preserved as much as possible, minimising the loss of information. Several approaches to this problem can be found in the literature. In particular, when the knowledge is represented by an ontology, two different families of frameworks have been developed in the literature in the past decades with numerous ideas in common but with little interaction between the communities: applications of AGM-like Belief Change and justification-based Ontology Repair. In this paper, we investigate the relationship between pseudo-contraction operations and gentle repairs. Both aim to avoid the complete deletion of sentences when replacing them with weaker versions is enough to prevent the entailment of the unwanted formula. We show the correspondence between concepts on both sides and investigate under which conditions they are equivalent. Furthermore, we propose a unified notation for the two approaches, which might contribute to the integration of the two areas