A temporal database (see Temporal Database) contains time-varying data. Time is an important aspect of all real-world phenomena. Events occur at specific points in time; objects and the relationships among objects exist over time. The ability to model this temporal dimension of the real world is essential to many computer applications, such as accounting, banking, econometrics, geographical information systems, inventory control, law, medical records, multi-media, process control, reservation systems, and scientific data analysis. Conventional databases represent the state of an enterprise at a single moment of time. Although the contents of the database continue to change as new information is added, these changes are viewed as modifications to the state, with the old, out-of-date data being deleted from the database. The current contents of the database may be viewed as a snapshot of the enterprise. When a conventional database is used, the attributes involving time are manipulated solely by the application programs, with little help

This paper applies important existing completeness notions to TSQL2 in

This is a draft of a manuscript of a postgraduate course taught at the Hong Kong University of Science and Technology in Spring 94. The course gives an introduction into the young and fascinating field of knowledge discovery in databases. The manuscript is suited for beginners who can leave out the more advanced sections, as well as people who would like to do research in this area. This manuscript is partly incomplete. Especially, the last section discussing approaches to learn knowledge involving time is missing. Contents 1 Introduction 2 1.1 Course Outline : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2 1.2 Basic Notions : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 3 1.3 A Case Study : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 6 1.4 Outlook : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 9 LIST OF FIGURES 2 2 Rule Languages 15 2.1 Proposit...

This paper investigates temporal integrity constraints in valid time databases, i.e. databases that capture the time-varying nature of the part of reality being modeled. We first provide a taxonomy of integrity constraints in (temporal) databases in order to establish a common terminology. The taxonomy identifies two classes of valid time integrity constraints: intrastate and interstate integrity constraints. Intrastate integrity constraints result from generalizing nontemporal integrity constraints. They guarantee the consistency of every snapshot of a valid time database. Interstate integrity constraints relate and constrain different valid time snapshots and, therefore, they are unique to the temporal dimension. ChronoLog, a query language based on first order predicate logic, can express both types of integrity constraints. Furthermore, timerestricted integrity constraints may be expressed in ChronoLog. Finally, we discuss the efficient checking of valid time integrity c...

We present a general approach for modelling temporal aspects of objects in a logic programming framework. Change is formulated in the context of a database which stores explicitly a record of all changes that have occurred to objects and thus (implicitly) all states of objects in the database. A snapshot of the database at any given time is an object-oriented database, in the sense that it supports an object-- based data model. An object is viewed as a collection of simple atomic formulas, with support for an explicit notion of object identity, classes and inheritance. The event calculus is a treatment of time and change in first-order classical logic augmented with negation as failure. The paper develops a variant of the event calculus for representing changes to objects, including change in internal state of objects, creation and deletion of objects, and mutation of objects over time. Implementation strategies for practical application to temporal object-oriented databases...

The maintenance of semantic integrity has been recognized as a cornerstone issue for the development of databases and knowledge bases alike. Despite the extensive research conducted during the last two decades, semantic integrity maintenance has yet to become a practical technology. Furthermore, the need for modeling evolving domains has given rise to challenging research issues relating to the incorporation of time in knowledge bases. In this thesis, we study the problem of maintaining the integrity of temporal deductive knowledge bases. We argue that existing approaches in either temporal or deductive databases do not address the problem in a satisfactory manner, nor do they deal with all the issues involved in a unified framework. At first, we propose an assertion language that permits us to express different types of temporal assertions that are not expressible in other formalisms. We define the notion of temporal constraint satisfaction in a bitemporal context. We then follow two ...

This article presents the theory and implementation of an Artificial Intelligence planner, CHICA. CHICA is a non-linear, domain independent planner based on techniques of computational logic. The representation language of the planner is Horn clause logic which is used to model event calculus, a logical theory of changing properties over time. The reasoning component is an abductive extension of SLDNF resolution for generating assumptions to prove a given goal. In event calculus, this procedure generates a plan of events and temporal relations necessary to prove the planning goal. CHICA uses domain contraints and techniques from contraint logic programming to efficiently implement inequality, as well as a specialized module to evaluate temporal relations. CHICA's generic search algorithm lets the implementor of a planning domain define a particular search strategy and specify domain heuristics to prune the search space. CHICA has solved a number of planning problems successfully: multiple robot block world problems, the assembly of a flashlight, and a room decoration problem. Extensions to classical AI-planning can be solved within the same framework, such as plan execution and replanning. keywords: planning, logic programming, event calculus Senior Scientist at SHAPE Technical Centre, The Hague, The Netherlands y Research Associate of the National Fund for Scientific Research, Belgium 1 1

Similarities between the concepts of time and uncertainty are worked out. Using a functional and object-oriented query language we present techniques of how to enhance a query language to manage time and/or uncertainty. These results can be used to define semantics for syntactically small but extremely powerful languages enhanced with two dimensions : time or any dimension with a total ordering, and uncertainty which can be interpreted in probabilistic or any other way. 1 Introduction Any piece of data can additionally be specified along two dimensions: ffl time, and ffl uncertainty. These two specifications are independent of the way the data is represented. For example, suppose it is given that a customer C will buy some portion of a mutual fund F . In whatever form this is represented, (i) either as the tuple (C; F ) in a relational table with name Buy, (ii) as a fact buy(C; F ), or (iii) in functional form as a function Buy mapping the customer C to the value F , two pieces of...

This paper deals with the problem of providing temporal deductive databases with an efficient implementation in a logic programming framework. We restrict our attention to historical databases based on Kowalski and Sergot's Event Calculus extended with context-dependency. The paper aims at being beneficial to both the theoretically-minded and the implementation-oriented research communities. It provides a mathematical analysis of the computational complexity of query and update processing in the Event Calculus, and proposes a cached version of the calculus that moves computational complexity from query to update processing, and features an absolute improvement of performance when contextdependency is added. 1 Introduction The paper deals with the problem of providing temporal deductive databases (TDDs) with an efficient implementation in a logic programming framework. TDDs provide the possibility of managing temporal information not only to retrieve information as it was stored in th...

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