Integrating data and knowledge from multiple heterogeneous sources --- like databases, knowledge bases or specific software packages --- is often required for answering certain queries. Recently, a powerful framework for defining mediated views spanning multiple knowledge bases by a set of constrained rules (cf. work of Kanellakis et. al. [27]) was proposed [39, 5, 26]. Within this paper, we investigate the materialization of these views by unfolding the view definition and the efficient maintenance of the resulting materialized mediated view in case of updates. Thereby, we consider two kinds of updates: updates to the view and updates to the underlying sources. For each of these two cases several efficient algorithms maintaining materialized mediated views are given. We improve on previous algorithms like the DRed algorithm [22] and introduce a new fixpoint operator WP which --- opposed to the standard fixpoint operator TP [19] --- allows us to correctly capture the update'...

During the process of updating a database, two interrelated problems could arise. On one hand, when an update is applied to the database, integrity constraints could become violated, thus falsifying database consistency. In this case, the integrity constraint maintenance approach tries to obtain additional updates to be applied to re-establish database consistency. On the other hand, when an update request consist on updating some derived predicate, a view updating mechanism must be applied to translate the update request into correct updates on the underlying base facts. In this paper, we propose a general framework to compare and classify current methods in the field of view updating and integrity constraint maintenance. In this sense, we classify them considering how they tackle with both problems and, we also state the main drawbacks these methods have. 1. Introduction Most databases, like relational or deductive ones, allow the definition of intentional information l...

Schema validation and view updating are database engineering problems which seem to differ significantly. Hence, for solving them, significantly different approaches are taken, usually. However, one of the contributions of this paper is: We show that any sound method for view updating can effectively be used also for validating schema specifications. We consider typical schema validation tasks such as checking schema satisfiability, liveliness of a predicate, reachability of partially specified states and redundancy of integrity constraint specifications, and we show how, with any sound method for view updating, these tasks can be tackled in a uniform way. For illustrating our point, we shortly recapitulate a concrete method for view updating and apply it to tackle these tasks. We emphasize that our general approach is independent of any particular method for view updating. Other contributions consists in refined concepts of schema satisfiability and integrity redundance. Both can be e...

In this paper we propose two interpretations of the event rules [Oli91] which provide a common framework for classifying and specifying deductive database updating problems such as view updating, materialized view maintenance, integrity constraints checking, integrity constraints maintenance, repairing inconsistent databases, integrity constraints satisfiability or condition monitoring. Moreover, these interpretations allow us to identify and to specify some problems that have received little attention up to now like enforcing or preventing condition activation. By considering only a unique set of rules for specifying all these problems, we want to show that it is possible to provide general methods able to deal with all these problems as a whole. 1 Introduction Deductive databases generalize relational databases by including not only base facts and integrity constraints, but also deductive rules. Using these rules, derived facts may be derived from facts explicitly stored. Among oth...

Two different approaches have been traditionally considered for dealing with the process of integrity constraints enforcement: integrity checking and integrity maintenance. However, while previous research in the first approach has mainly addressed efficiency issues, research in the second approach has been mainly concentrated in being able to generate all possible repairs that falsify an integrity constraint violation. In this paper we address efficiency issues during the process of integrity maintenance. In this sense, we propose a technique which improves efficiency of existing methods by defining the order in which maintenance of integrity constraints should be performed. Moreover, we use also this technique for being able to handle in an integrated way the integrity constraints enforcement approaches mentioned above. 1. Introduction Database updating has attracted a lot of research during last years [Abi88]. Several problems may arise when updating a deductive database [TU95]. O...

We address efficiency issues during the process of integrity maintenance. In this sense, we propose a technique that improves efficiency of existing methods by defining the order in which maintenance of integrity constraints should be performed. Moreover, we integrate view updating into integrity maintenance and we propose a technique for translating view updates efficiently, aimed at reducing the number of alternatives considered during the process of view updating and the EDB accesses required to perform this translation. 1. Introduction A deductive database is called consistent if it satisfies a set of integrity constraints. When applying a transaction, database consistency may be violated. That is, the transaction may falsify some integrity constraint. An approach to deal with this problem is that of integrity maintenance [ML91, Wt93, Ger94, CFPT94, TO95, Maa98, Sch98], which is concerned with trying to repair integrity constraints violations by performing additional updat...

Abstract. This paper elaborates on scenarios for collaborative knowledge creation in the spirit of the trialogical learning paradigm. According to these scenarios the group knowledge base is formed by combining the knowledge bases of the participants according to various methods. The provision of flexible methods for defining various aspects of the group knowledge is expected to enhance synergy in the knowledge creation process and could lead to the development of tools that overcome the inelasticities of the current knowledge creation practices. Subsequently, these scenarios are projected to various knowledge representation frameworks and for each one of them the paper analyzes and discusses related techniques and identifies issues that are worth further research. 1

An important problem that arises when updating a deductive database is the one related to integrity constraints maintenance. That is, given a consistent database and an update request, to obtain all possible ways of updating the base facts such that the request is satisfied while consistency of the database is maintained. This problem becomes more complex when view updates may also be requested since these updates must be translated into base fact updates. In this paper we present a method for providing automatic support in these situations. Our method takes into account information about the keys of the predicates and it is able to handle updates which consist of a set of insertions, deletions and/or modifications of base and derived predicates. Our interest in this paper is to describe the current status of our work towards providing an effective and efficient method for updating consistent deductive databases. 1. Introduction Deductive databases generalize relational databases by in...

We show that database schema validation and update processing problems such as view updating, materialized view maintenance, integrity constraint checking, integrity constraint maintenance or condition monitoring can be classified as problems of either abductive or deductive nature, according to the reasoning paradigm that inherently suites them. This is done by performing abductive and deductive reasoning on the event rules (Olivé 1991), a set of rules that define the difference between consecutive database states In this way, we show that it is possible to provide methods able to deal with all these problems as a whole. We also show how some existing general deductive and abductive procedures may be used to reason on the event rules. In this way, we show that these procedures can deal with all database schema validation and update processing problems considered in this paper. 1

In this paper, we study the problem of incremental maintenance of materialized views when the view definitions are allowed to contain: (a) constraints, and (b) wellfounded modes of negation. A materialized view in our framework consists of a set of constrained non-ground tuples. We develop incremental algorithms to compute such non-ground materialized well-founded views, extending previous results of Gottlob et. al. and Eiter et. al. With respect to (b), previous attempts at view maintenance have been limited to the case when stratified negation is used. In contrast, in this paper, we allow arbitrary (stratified and/or unstratified) usage of negation. Recursive views are also allowed. We develop a view maintenance algorithm called WF-Red for handling updates in such cases. WF-Red takes two parameters as input -- a list of insertions and a list of deletions. To handle insertions, the list of deletions is kept empty and vice-versa. The algorithm correctly handles both insertions and del...