Paola Inverardi

Improving Integrity Constraint Checking in Deductive Databases

In this paper the description of a new method for integrity constraints checking in deductive databases is given and its correctness is proved. Our method extends and integrates two well known approaches in the literature, namely [Lloyd&Topor 85], [Lloyd&Topor 86], [Lloyd et al. 87] that has been proposed for stratified databases [Apt et al. 87], and [Nicolas 82] that was instead proposed for relational databases. Like in the other approaches we assume that the database satisfies the integrity constraints before the update and, therefore, any new violation of the constraints must involve the update, so that, it will be sufficient to check the instances of those constraints which could be invalidated by the update. Our method tries to minimize, as much as possible, the number of constraint instances to be checked, it works on stratified databases, thus including definite and hierarchical databases, and on the same kind of constraint formulas of [Lloyd et al. 87]. The method can be splitted into four steps: First step: a certain number of sets of atoms is defined to obtain a set of atoms which could falsify the integrity constraints. These sets contain all atoms that falsifies the integrity constraint. Even if inspired by [Lloyd et al. 87] the definition of the sets is different, the number of atoms computed is less than those computed with that method and, furthermore they are more instantiated. Second step: two set of substitutions One w and ifnew are defined so that each substitution contained in one of these sets is the mgu of an atom which is part of an integrity constraint W and of an atom included in one of the sets computed in the first step. This second step ends with the generation of instances of the integrity constraint formula W obtained by applying the substitutions in ®new U ~?new to W itself. Third step: like in [Nicolas 82] we try to simplify the obtained instances of W with the atoms pre-evalutation and with the application of the absorption rules. Fourth step: by using the SLDNF we try to prove that each simplified instance is a logical conseguence of the completion of the database.

Graphics by a Logic Database Management System

Abstract The GEDBLOG system allows applications which manipulate graphic objects to be developed following a declarative definitional style. GEDBLOG supports the consistent design and prototyping of graphic applications through an incremental development and makes it possible to guarantee automatically that the application meets its specifications. Typical GEDBLOG applications have graphics as their characterizing element and can be found, for example, in the CAD/CAM, visual languages or graphical interface areas. The system is obtained by integrating a graphical data language in an existing logic database management system, EDBLOG, so that graphic and non-graphic information is handled in a uniform declarative way.

Enhancing configuration facilities in software development: a logic approach

The paper focuses on the suitability and advantages of a Logic Data Base approach to manage configurational aspects within Programming Environments. It describes part of a work which proposes Logic Data Bases as effective tools to be integrated with existing programming environments to increase their formalization and automation capabilities. In order to present the idea and its implications, we discuss, as a practical example, the integration of a prototype Logic DBMS (EDBLOG) with a Unix-like environment for configuration management. In that framework, a possible realization of the Make facility is shown. The advantages of the proposed approach are mainly concerned with the easiness of extention of the programming environment and of the configuration environment to deal with concepts which, in general, are very expensive to provide,e.g. histories and versions management.

Selective Refutation of Integrity Constraints in Deductive Databases

In this paper we have presented a method that allows the selection of those branches of a derivation tree that contain a specific clause as input clause. We have applied such method to integrity constraint checking but it seems useful in other application areas as well.

Using Logic Databases in Software Development Environments

The paper discusses a role that logic programming can play in programming development environments. In particular, the suitability of logic databases to handle a specific programming development activity, notably configuration, is presented according to the experience gained while using a prototype logic database to support Ada-like configuration facilities [Asirelli 87a] and a Unix-like make facility [AsirelIi 87b]. The work reported in the paper is part of a more general project whose aim is to propose logic data bases as effective tools to be used as project databases. To this respect it is useful to point out that the relations induced on modules by the configuration activity are typical examples of relations that must be dealt with by a project database.

Prototyping in the GEDBLOG system

The paper presents a system to support prototyping in a deductive database management context. First, the basic entities and activities involved in the prototyping process are recast into a knowledge base framework. Then, the system GEDBLOG is introduced, illustrating how its features can be used to provide a suitable support to the defined environment. The design and prototyping of a graphic application demonstrates the approach.<<ETX>>