The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
LOGIDATA+ is part of the subproject “Advanced Database Systems” of the project “Information Systems and Parallel Computation”, of the Italian research council. The aim of LOGIDATA+ is the definition of advanced database systems, which significatively extend the functionalities of the current systems, with specific reference to the application areas for which relational systems are not considered satisfactory...
A recent direction of database research has been focused on integrating logic programming and object orientation. The rationale of such integration stems from two arguments; on one hand, object-orientation brings powerful data modeling capabilities by adding semantic and structural complexity to value-based relational databases. On the other hand, logic programming languages provide means for...
The LOGIDATA+ data model is presented. It is value-based, object-based, and functional at the same: it involves classes (with object-identity), relations (value based), and functions. Classes can be referred to in relations and functions. Is-a relationships can be defined on classes. Complex values can be built by means of the recursive use of set, tuple, and sequence constructors. As usual in database...
A language for the LOGIDATA+ model is presented. The language is rule-based and allows for the management of complex structures, classes, hierarchies and data functions. Negation is allowed in the body of rules. The semantics is based on a fixpoint operator and represents an extension of ordinary declarative-language semantics. The main issue is the management of oid-invention, that is, the creation...
Expressive power and flexibility of the LOGIDATA+ model and language are explored. We analyze a program for travel agencies: the problem we consider is concerned with the construction of travels on the basis of the clientś specifications. The program queries the database and generates a report with all the available choices in terms of transfers and accomodations. The scheme and the clauses use a...
This paper deals with the definition of update language facilities for the purely object-oriented subset of the Logidata+ model. Several update operators are introduced, which correspond to basic manipulations of complex data entities with object identity. These operators can be used in rules bodies for specifying complex update transactions. The resulting language is first informally presented by...
Taxonomic reasoning is a typical inference task performed by many AI knowledge representation systems. We illustrate the effectiveness of taxonomic reasoning techniques as an active support to knowledge acquisition and schemas design in the advanced database environment LOGIDATA+, supporting complex objects and a rule-based language. The developed idea is that, by extending complex object data models...
In this paper we give a syntax and define a denotational semantics for describing classes in LOGIDATA*, and give a subsumption algorithm that is sound, complete, and polynomial. The syntax allows us to describe both primitive and defined acyclic classes by means of the tuple and set type constructors; in particular, it is also possible to state cardinality constraints on sets. Semantics is defined...
This paper shows the subsumption computation techniques for a LOGIDATA+ schema allowing cyclic definitions for classes. The formal framework LOGIDATACYC*, which extends LOGIDATA* to perform taxonomic reasoning in the presence of cyclic class definitions is introduced. It includes the notions of possible instances of a schema; legal instance of a schema, defined as the greatest fixed-point of possible...
Recent years have witnessed a continuous evolution of database models towards richer and more expressive paradigms. Along the line of enriching the modeling capabilities, Object-Oriented databases (OODBs) have been introduced. In this paper, we propose a further enhancement to OODB models aiming at enriching the database schema by explicitly declaring semantic integrity constraints therein. ...
Negative programs are logic programs where negation may arise also in the head of rules and have been recently introduced to handle exceptions to general rules. In this paper we present efficient techniques for computing the intended model of stratified negative programs.
Total stable models provide a powerful semantics for DATALOG− programs which increases the expressive power of current database query language by means of non-determinism. An efficient algorithm for determining one of stable models of a DATALOG− programs, if any, is presented so that stable models may have also a practical interest.
This paper describes a proposal for knowledge modularization in a logic language. Our aim is to define structuring mechanisms for the integration and composition of modules in order to provide software reusability, clean problem definition and non-standard programming techniques. The proposed mechanisms include the ability to define modules and connections between them. A program module can be combined...
In this paper we present the Logidata Object Algebra (LOA), an algebra for complex objects which has been developed within LOGIDATA+, a national project funded by the Italian National Research Council, as an internal language in a prototype system for the management of extended relational databases with complex object types. LOA is a set-oriented manipulation language which was conceived as an internal...
In this paper we present a prototype system based on the LOGIDATA+ model, hence supporting a rule based language on a data model with structured data types, object identity and sharing. The system has an interactive user interface, with a units interaction composed by LOGIDATA+ programs, that can extract information from the knowledge base and/or modify the schema. A program consists of a set of rules...
In this paper we describe MOOD, a system which may be used to easily and efficiently build C++ programs accessing a relational database. MOOD has its own data model, which is Object-Oriented, and supports object identity, generalization hierarchies, and object sharing; by processing schema definitions, the MOOD system builds a relational schema and a C++ Class Library that enable the interaction between...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.