17,672 research outputs found
Integrity constraints in deductive databases
A deductive database is a logic program that generalises the concept of a relational database. Integrity constraints are properties that the data of a database are required to satisfy and in the context of logic programming, they are expressed as closed formulae. It is desirable to check the integrity of a database at the end of each transaction which changes the database. The simplest approach to checking integrity in a database involves the evaluation of each constraint whenever the database is updated. However, such an approach is too inefficient, especially for large databases, and does not make use of the fact that the database satisfies the constraints prior to the update.
A method, called the path finding method, is proposed for checking integrity in definite deductive databases by considering constraints as closed first order formulae. A comparative evaluation is made among previously described methods and the proposed one. Closed general formulae is used to express aggregate constraints and Lloyd et al. 's simplification method is generalised to cope with these constraints.
A new definition of constraint satisfiability is introduced in the case of indefinite deductive databases and the path finding method is generalised to check integrity in the presence of static constraints only. To evaluate a constraint in an indefinite deductive database to take full advantage of the query evaluation mechanism underlying the database, a query evaluator is proposed which is based on a definition of semantics, called negation as possible failure, for inferring negative information from an indefinite deductive database.
Transitional constraints are expressed using action relations and it is shown that transitional constraints can be handled in definite deductive databases in the same way as static constraints if the underlying database is suitably extended. The concept of irnplicit update is introduced and the path finding method is extended to compute facts which are present in action relations. The extended method is capable of checking integrity in definite deductive databases in the presence of transitional constraints.
Combining different generalisations of the path finding method to check integrity in deductive databases in the presence of arbitrary constraints is discussed. An extension of the data manipulation language of SQL is proposed to express a wider range of integrity constraints. This class of constraints can be maintained in a database with the tools provided in this thesis
The Events method for temporal integrity constraint handling in bitemporal deductive databases
A bitemporal deductive database is a deductive database that supports valid and
transaction time. A temporal integrity constraint deals
with only valid time, only transaction time or both times. A set of facts to be
einserted and deleted in a bitemporal deductive database can
be done in a past, present or future valid time and at current transaction time.
The temporal integrity constraint handling in bitemporal
deductive databases causes that the maintenance of consistency becomes more
complex than another databases. The $events method$ for handling temporal integrity constraints.
Finally, we present the interaction between the above-mentioned conceptual and
representational data models.Postprint (published version
A common framework for classifying and specifying deductive database updating problems
Several problems may arise when updating a deductive database. Up to now,
the general approach of the research related to deductive database updating problems
has been to provide specific methods for solving particular problems. However, ali
these methods are explicitly or implicitly based on a set of rules that define the
changes that occur in a transition from an old state of a database to a new, updated
state. Therefore, these rules provide the basis of a framework for classifying and
specifying these problems.
In this paper we propose to use the event rules [Oli91], which explicitly define
the insertions and deletions induced by an update, for such a basis. We also define
two interpretations of these rules 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 sorne problems that have received little attention up to now
like enforcing or preventing condition activation. By considering only a uniqu~ 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
Towards Intelligent Databases
This article is a presentation of the objectives and techniques
of deductive databases. The deductive approach to databases aims at extending
with intensional definitions other database paradigms that describe
applications extensionaUy. We first show how constructive specifications can
be expressed with deduction rules, and how normative conditions can be defined
using integrity constraints. We outline the principles of bottom-up and
top-down query answering procedures and present the techniques used for
integrity checking. We then argue that it is often desirable to manage with
a database system not only database applications, but also specifications of
system components. We present such meta-level specifications and discuss
their advantages over conventional approaches
Extending the synthesis of update transaction programs to handle existential rules in deductive databases
We propose a new method for generating consistency-preserving transaction programs for (view)
updates in deductive databases. The method augments the deductive database schema with a set of
transition and intemal events rules, which explicitly define the database dynamic behaviour in front of
a database update. At transaction-design-time, a formal procedure can use these rules to automatically
generate parameterised transaction programs for base or view-update transaction requests. This is
done in such a way that those transactions will never take the database into an inconsistent state. In
this paper we extend a previous version of the method by incorporating existentially defined rules.
Within this context, synthesis outputs and processes are provided. Toe method, implemented in
Prolog using meta-programming techniques, draws from our previous work in deductive databases,
particularly in view updating and integrity constraints checking
Structuring the process of integrity maintenance (extended version)
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 constraintsPostprint (published version
A Review of integrity constraint maintenance and view updating techniques
Two interrelated problems may arise when updating a database. On one
hand, when an update is applied to the database, integrity constraints
may become violated. In such case, the integrity constraint maintenance
approach tries to obtain additional updates to keep integrity
constraints satisfied. On the other hand, when updates of derived or
view facts are requested, a view updating mechanism must be applied to
translate the update request into correct updates of the underlying base
facts.
This survey reviews the research performed on integrity constraint
maintenance and view updating. It is proposed a general framework to
classify and to compare methods that tackle integrity constraint
maintenance and/or view updating. Then, we analyze some of these methods
in more detail to identify their actual contribution and the main
limitations they may present.Postprint (published version
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