Antonio L. Furtado

An algebra of quotient relations

An algebra which operates on partitioned relations is developed. Relation partitioning is achieved by defining equivalence relations on n-ary relations. It is shown that the algebra is as powerful as the original relational algebra, having the advantage of a set-processing capability. This feature provides both greater flexibility in query specification and efficient query processing.

Permitting updates through views of data bases

Abstract Providing different views (logical images of the structure of a data base) to various users creates the problem of determining how update operations expressed in terms of the views should affect the stored form of the data base. For data bases with a relational organization, we indicate the effects of a wide range of update operations on views. We conclude that some operations must be prohibited in order to assure harmonious interactions among data base users, but that many other operations can be allowed even though the structure of the view may differ substantially from the actual structure of the data base. We consider views not only as “windows” through which to see a data base in a particular way, but also as “shades” to conceal and protect information, and as “screens” to intercept any update operations that could leave the stored form of the data base in an unacceptable state.

Formal techniques for data base design

1 General Introduction - Two Approaches to Formal Data Base Design.- A - Application-Oriented Approach.- 2 Introduction to Part A.- 3 An Informal Outline.- 3.1 Information Level.- 3.2 Functions Level.- 3.3 Representation Level.- 3.4 Placing the Formalisms.- 4 The Information Level - The Use of Logical Formalisms.- 4.1 Logical Formalisms.- 4.2 An Example.- 5 The Functions Level - The Use of Algebraic Formalisms.- 5.1 Algebraic Formalisms.- 5.2 Obtaining a Functions Level Specification - An Example.- 5.3 First to Second Level Refinements.- 5.4 Proof of Correctness of the Refinement - An Example.- 6 The Representation Level -The Use of a Programming Language Formalism.- 6.1 Programming Language Formalism.- 6.1.1 Syntax - The Use of a Grammatical Formalism.- 6.1.2 Semantics - The Use of a Denotational Formalism.- 6.2 Obtaining a Representation Level Specification - An Example.- 6.3 Second to Third Level Refinements.- 6.4 Proof of Correctness of the Refinement - An Example.- B - Semantic Data Models.- 7 Introduction to Part B.- 8 The Logical Database Model.- 8.1 The Semantic Framework.- 8.1.1 Reality and the Real World States.- 8.1.2 The Natural Language State Description.- 8.1.3 The Abstract Model and the Standard Interpretation.- 8.1.4 The Logical State Description and the Interpretation IDB.- 8.1.5 Conventional Data Bases - The Syntactical View.- 8.2 The Logical Data Definition Language.- 8.2.1 Type Declarations.- 8.2.2 The Clause of a Type Declaration.- 8.2.3 The Clause of a Type Declaration.- 8.2.4 The Clause of a Type Declaration.- 8.2.5 Relation Declarations.- 8.2.6 The Clause of Relation Declarations.- 8.2.7 The Clause of Relation Declarations.- 8.3 The Logical Data Language LDL.- 9 The Entity-Relationship Model.- 9.1 The Entity-Relationship-Value Concept.- 9.1.1 Level 1: Entities, Relationships, Values.- 9.1.2 Level 2: Entity-Relationship Diagram.- 9.1.3 Level 3: Entity Relations, Relationship Relations and Relation Tables.- 9.2 Data Types and the Entity-Relationship Model.- 9.2.1 Generalization/Specialization.- 9.2.2 Aggregation.- 9.2.3 Grouping.- 9.3 Existence and Identification Constraints in the Extended ER-Model.- 9.3.1 Constraints Related to Generalization/Specialization.- 9.3.2 Constraints Related to Aggregation.- 9.3.3 Constraints Related to Grouping.- 9.4 An Example Using the Extended ER-Model.- 10 The Temporal Hierarchic Model.- 10.1 The Basic Concepts of THM.- 10.2 The Notions of Time in THM.- 10.3 The Operational Facilities of the Temporal Hierarchic Model.- 10.3.1 The Basic State Manipulation Actions.- 10.3.2 Complex State Manipulation Actions.- 11 Conclusion.- 12 References.- 13 Subject Index.

Towards multi-level and modular conceptual schema specifications

The specification of the conceptual schema for a data base application is divided into levels. It is argued that, at the highest level, a direct description of the characteristics of the information kept in a data base and of the constraints governing their existence and transformation of its components characterizes what a particular data base is in a more fundamental way (hence at a higher and more stable level) than the operations that happen to be used for data base manipulation. At a next lower level a specification based on operations, using the encapsulation strategy of abstract data types, is introduced, followed by a specification based on representations used in semantic data models. The discussion includes constraints involving temporal aspects. Modularization is also discussed as another dimension in the specification process, orthogonal to the division into levels.

Instance-Based OWL Schema Matching

Schema matching is a fundamental issue in many database applications, such as query mediation and data warehousing. It becomes a challenge when different vocabularies are used to refer to the same real-world concepts. In this context, a convenient approach, sometimes called extensional, instance-based or semantic, is to detect how the same real world objects are represented in different databases and to use the information thus obtained to match the schemas. This paper describes an instance-based schema matching technique for an OWL dialect. The technique is based on similarity functions and is backed up by experimental results with real data downloaded from data sources found on the Web.

A software tool for modular database design

A modularization discipline for database schemas is first described. The dicipline incorporates both a strategy for enforcing integrity constraints and a tactic for organizing large sets of database structures, integrity constraints, and operations. A software tool that helps the development and maintenance of database schemas modularized according to the discipline is then presented. It offers a user-friendly interface that guides the designer through the various stages of the creation of a new module or through the process of changing objects of existing modules. The tool incorporates, in a declarative style, a description of the design and redesign rules behind the modularization discipline, hence facilitating the incremental addition of new expertise about database design.

Automatic Video Editing for Video-Based Interactive Storytelling

The development of interactive narratives with the quality of feature films is the central challenge of what we can name Video-Based Interactive Storytelling. A promising approach to this question is the use of prerecorded videos with real actors. Amongst several technical challenges, this approach firstly requires automatic video editing methods for interactive narratives. However, this is a critical issue not fully covered in the literature. In this paper, we present a real-time editing method for interactive storytelling systems, which automatically generates the most adequate shot transitions, swaps video segments to avoid jump cuts, and creates adequate looping scenes. Moreover, these features consider the characteristics of the ongoing story.

Analogy by generalization—and the quest of the grail

It is argued that a powerful kind of reasoning by analogy is provided by combining unification with most specific generalization. A revised version of an existing algorithm to compute the most specific generalization of terms is presented, which decides correctly whether or not new variables should be introduced in each case. Both unification and most specific generalization are extended to frames. It is indicated, as a research goal, the extension of these processes to more complex forms of knowledge representation, a particularly challenging example being the comparison of the structures of literary narratives.

Constructing Libraries of Typical Plans

Databases able to represent, not only facts, but also events in the mini-world of the underlying information system can be seen as repositories of narratives about the agents and objects involved. The events treated in our approach are those attributed to executions of predefined application-oriented operations. This work addresses the identification of typical plans adopted by agents, by analysing a Log registering the occurrence of events, as represented by executions of such operations. The analysis is done by applying a previously formulated set of goal-inference rules to sequences of interrelated events, called plots, taken from the Log. The obtained Library of Typical Plans, together with the goal-inference rules, constitute the behavioural level of our proposed three-level conceptual schemas for the specification of information systems. A prototype Prolog implementation of the method for extracting typical plans is operational. A simple example is used to illustrate the discussion.

On the Description of Database Transition Constraints Using Temporal Languages

A family of formal languages that extends classic temporal logic with mechanisms to define new modalities is described. The languages are sufficiently flexible to express a wide range of database transition constraints, that is, restrictions on what sequences of database states are meaningful. They are useful in the context of a database design methodology where the first level of specification consists of a purely declarative definition of both static and transition constraints. A sequence of results about the solvability of the decision problem of these languages is also presented that helps assess the expressive power of the languages.