Strategy for processing multivariable queries in the database management system INGRES is considered. The general procedure is to decompose the query into a sequence of one-variable queries by alternating between (a) reduction: breaking off components of the query which are joined to it by a single variable, and (b) tuple substitution: substituting for one of the variables a tuple at a time. Algorithms for reduction and for choosing the variable to be substituted are given. In most cases the latter decision depends on estimation of costs; heuristic procedures for making such estimates are outlined.

This paper presents VIQING, an environment for expressing queries via direct manipulation of data visualizations. VIQING provides a simple graphical interface for connecting visualizations, and has the expressive power of the basic relational operators select, project and join. VIQING has been implemented in the Tioga DataSplash visualization system to provide a seamless integration of querying and browsing. The resulting system is unique in providing a unified visual interface for developing database applications, encompassing both querying and data visualization. Key Words: database visualization, graphical query languages, direct-manipulation interfaces 1. Introduction Database systems are hard to use. Untrained users often find query interfaces frustrating and even trained database users frequently have difficulty analyzing the results of queries. Despite over 25 years of research in this area, these problems persist today. The goal of the Tioga project [14] has been to address th...

Abstract-We propose a technique for specifying universal quantification and existential quantification (combined with negation) in a two-dimensional (graphical) database query language. Unlike other approaches that provide set operators to simulate universal quantification, this technique allows a direct representation of universal quantification. We present syntactic constructs for specifying universal and existential quantifications, two-dimensional translation of universal quantification to existential quantification (with negation), and translation of existentially quantified two-dimensional queries to relational queries. The resulting relational queries can be processed directly by many existing database systems. Traditionally, universal quantification has been considered a difficult concept for typical database programmers. We claim that this technique renders universal quantification easy to understand. To substantiate this claim, we provide a simple, easy-to-follow guideline for constructing universally quantified queries. We believe that the direct representation of universal quantification in a two-dimensional language is new and that our technique contributes significantly to the understanding of universal quantification in the context of database query languages. Index Terms- Universal quantification, existential quantification, graphical query languages, databases, relational calculus, entity-relationship model. I.

Graphical user interfaces have become very popular for database systems since they increase the usability of these applications. The functionality and ease- of-use of the graphical user interface, however, depend on the expressiveness and complexity of the underlying data model. With the advent of new database technology based on powerful data models like the object-oriented data model new challenges and new opportunities are posed in user interface design. In this paper we discuss critical issues of graphical user interface development for object-oriented database systems. 1 Introduction We are witnessing a change of attitude concerning the importance of the user interface of an application compared to the application itself. As Dertouzous pointed out in his plenary address at CHI'90 [18], nowadays, about 70% of an application's code is devoted to user interface handling, and only 30% deals with the actual application. With the advent of powerful bit-mapped graphic workstations and in...