The Problem Of Incomplete Information In Relational Databases

Reviews of Environmental Contamination and Toxicology publishes authoritative reviews on the occurrence, effects, and fate of pesticide residues and other environmental contaminants. It will keep you informed of the latest significant issues by providing in-depth information in the areas of analytical chemistry, agricultural microbiology, biochemistry, human and veterinary medicine, toxicology, and food technology.

Abstract: "In practice it is often the case that the available information is incomplete with respect to the information that is supposed to be recorded in the database. We consider the problems raised by this situation in the context of the relational model. The basic semantic assumption is that an incomplete database is a set of complete databases (relations). We show that there are two natural lattice structures on the set of all sets of relations. These lattices enable us to give precise meanings to operations performed on incomplete databases. The operations are querying, dependency enforcement and updates. There are several candidate tools for storing and manipulating databases with incomplete information. We focus on generalizations of relations

The chase has long been used as a central tool to analyze dependencies and their effect on queries. It has been applied to different relevant problems in database theory such as query optimization, query containment and equivalence, dependency implication, and database schema design. Recent years have seen a renewed interest in the chase as an important tool in several database applications, such as data exchange and integration, query answering in incomplete data, and many others. It is well known that the chase algorithm might be non-terminating and thus, in order for it to find practical applicability, it is crucial to identify cases where its termination is guaranteed. Another important aspect to consider when dealing with the chase is that it can introduce null values into the database, thereby leading to incomplete data. Thus, in several scenarios where the chase is used the problem of dealing with data dependencies and incomplete data arises. This book discusses fundamental issues concerning data dependencies and incomplete data with a particular focus on the chase and its applications in different database areas. We report recent results about the crucial issue of identifying conditions that guarantee the chase termination. Different database applications where the chase is a central tool are discussed with particular attention devoted to query answering in the presence of data dependencies and database schema design. Table of Contents: Introduction / Relational Databases / Incomplete Databases / The Chase Algorithm / Chase Termination / Data Dependencies and Normal Forms / Universal Repairs / Chase and Database Applications

Time is ubiquitous in information systems. Almost every enterprise faces the problem of its data becoming out of date. However, such data is often valu able, so it should be archived and some means to access it should be provided. Also, some data may be inherently historical, e.g., medical, cadastral, or ju dicial records. Temporal databases provide a uniform and systematic way of dealing with historical data. Many languages have been proposed for tem poral databases, among others temporal logic. Temporal logic combines ab stract, formal semantics with the amenability to efficient implementation. This chapter shows how temporal logic can be used in temporal database applica tions. Rather than presenting new results, we report on recent developments and survey the field in a systematic way using a unified formal framework [GHR94; Ch094]. The handbook [GHR94] is a comprehensive reference on mathematical foundations of temporal logic. In this chapter we study how temporal logic is used as a query and integrity constraint language. Consequently, model-theoretic notions, particularly for mula satisfaction, are of primary interest. Axiomatic systems and proof meth ods for temporal logic [GHR94] have found so far relatively few applications in the context of information systems. Moreover, one needs to bear in mind that for the standard linearly-ordered time domains temporal logic is not re cursively axiomatizable [GHR94]' so recursive axiomatizations are by necessity incomplete.

This book constitutes the thoroughly refereed post-proceedings of the Second International Workshop on Semantics in Databases, held in Dagstuhl Castle, Germany, in January 2001. The 10 revised full papers presented together with an introduction by the volume editors were carefully selected during two rounds of reviewing. Among the aspects of database semantics discussed are semantic constraints, paraconsistency, logic foundations of databases, ER modeling, type hierarchies, null values, consistency enforcement, logic-based pattern languages, and semantic classification of queries. Among the classes of databases dealt with are deductive databases, relational databases, distributed information systems, and tree-structured data.

Uncertainty Management in Information Systems: From Needs to Solutions is a book about how information systems can be made to manage information permeated with uncertainty. This subject is at the intersection of two areas of knowledge: information systems is an area that concentrates on the design of practical systems that can store and retrieve information; uncertainty modeling is an area in artificial intelligence concerned with accurate representation of uncertain information and with inference and decision-making under conditions infused with uncertainty. The first part of this book describes issues and challenges in the area of imperfect information that confront information systems, and the second part covers the principal theories for modeling imperfect information, and shows how these theories may be adapted to information systems. All chapters are original contributions and present solutions that have been applied and the experiences that have been gained from those solutions. The material has been closely edited by the book's editors for content, consistency and style. This authoritative book is state-of-the-art coverage of `Uncertainty Management in Information Systems'.

This book constitutes the proceedings of the 9th International Symposium on Foundations of Information and Knowledge Systems, FoIKS 2016, held in Linz, Austria, in March 2016. The 14 revised full papers presented papers were carefully reviewed and selected from 23 submissions. The papers address various topics such as reasoning about beliefs, uncertainty, incompleteness, and inconsistency, inference and problem solving, querying and pattern mining, dealing with knowledge, logics and complexity.