During several years of friendship and joint work with Claudio, starting from the teaching experience we had in the University of Calabria at the beginning of our academic careers, we shared a lot ...

"ItAIS (the Italian chapter of AIS) remembers Claudio." European Journal of Information Systems, 14(5), pp. 454–455

In geographic maps, objects are represented in a context extremely rich of relationships among them, either one-to-one or many-to-many. Unfortunately, all these relationships can not be directly represented in the database scheme. Nevertheless, it should be possible to show them to the user during the interaction. To manage this problem, the authors refer to a two-level database architecture with an object-oriented data model at the bottom level (the logic level), and an interaction model at the top level. The spatial data model given is an essential part of the interaction model. The spatial data model is a conceptual tool that enhances the object-oriented model with spatial relationships between objects. The basic objectives of the spatial data model are outlined: to point out the relationships among objects to be shown in the views, to define data structures suitable for navigating among database objects, and to provide a simple and powerful calculus for posing spatial queries against the database.>

Distance-hereditary graphs have been introduced by Howorka and studied in the literature with respect to their metric properties. In this paper several equivalent characterizations of these graphs are given: in terms of existence of particular kinds of vertices (isolated, leaves, twins) and in terms of properties of connections, separators, and hangings. Distance-hereditary graphs are then studied from the algorithmic viewpoint: simple recognition algorithms are given and it is shown that the problems of finding cardinality Steiner trees and connected dominating sets are polynomially solvable in a distance-hereditary graph.

A new dynamic approach to the problem of determining the correct interpretation of a logically independent query to a relational database is described. The proposed disambiguating process is based on a simple user-system dialogue that consists in a sequence of decisions about the relevance (or not) of an attribute with respect to the user interpretation

In this paper the problem of minimal representations for particular classes of directed hypergraphs is analyzed. Various concepts of minimal representations of directed hypergraphs (called minimal equivalent hypergraphs) are introduced as extensions to the concepts of transitive reduction and minimum equivalent graph of directed graphs. In particular, we consider equivalent hypergraphs which are minimal with respect to all parameters which may be adopted to characterize a given hypergraph (number of hyperarcs, number of adjacency lists required for the representation, length of the overall description,etc.). The relationships among the various concepts of minimality are discussed and their computational properties are analyzed. In order to derive such results, a graph representation of hypergraphs is introduced.

Article Free Access Share on Chordality properties on graphs and minimal conceptual connections in semantic data models Authors: Giorgio Ausiello View Profile , Alessandro D'Atri View Profile , Marina Moscarini View Profile Authors Info & Claims PODS '85: Proceedings of the fourth ACM SIGACT-SIGMOD symposium on Principles of database systemsMarch 1985 Pages 164–170https://doi.org/10.1145/325405.325426Online:25 March 1985Publication History 0citation73DownloadsMetricsTotal Citations0Total Downloads73Last 12 Months2Last 6 weeks1 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

The acyclicity degree of a relational database scheme is an interesting topic due to several desirable properties of the corresponding database [5,16]. In this paper a simple and homogeneous way to characterize the acyclicity degree of a database scheme is given. The method is based on the existence in all acyclic database schemes of a nonempty set of relation schemes that satisfy a "pruning predicate", which is a property similar to the property satisfied by the leaves in an ordinary tree. This fact implies that such relation schemes may be eliminated using a recursive pruning algorithm in order to determine the acyclicity degree. Furthermore, if we use an incremental step by step design methodology, enriching the scheme one relation at a time, the pruning predicate suggests a set of properties that have to be verified by the new relation scheme in order to preserve the acyclicity degree of the database scheme.

This paper concerns query answering in relational databases. We assume a universe U of attributes and a set of values associated with each attribute. A database scheme is a given collection R = {1, 2, ..., n} of subsets of U, called relation schemes. A query in R is any subset of U. We call "context" any joinable subset of R. An unambiguous context is one in which a query receives the same answer independently of the subcontext used for the computation. A formal treatment of unambiguous contexts is presented and it is shown that they provide a suitable basis for discussing the universal relation assumption, the relationship uniqueness assumption, maximal objects, and other related concepts.

A graph-theoretic approach for the representation of functional dependenoes in relauonal databases is introduced and applied in the construction of algorithms for manipulating dependencies.This approach allows a homogeneous treatment of several problems (closure, minimization, etc.), which leads to simpler proofs and, m some cases, more efficient algorithms than in the current literature.