On the Expressive Power of Graphical Query Languages
Tiziana Catarci · 1991
In this paper a comparison is presented between the expressive power of generic graphical mechanisms and the various classes of queries (first-order, fixpoint, programming). A precise evaluation of the expressive power of the languages based on such mechanisms (i.e.purely graphical query languages) is shown. Moreover, an informal analysis is provided relatively to the more general class of the visual query languages, supporting also iconic interaction. 1. INTRODUCTION An important design issue in databases is to find an efficient and intuitively appealing query language which allows for expressing all the computable queries (see [23]). It is a well known fact that the graphics represents a friendly mechanism for the humancomputer interaction. In these years, many graphical query languages have been proposed, based on intensional (E-R diagram: GUIDE [34], GORDAS [20, 19], QBD * [7, 4], Pasta-3 [24], etc.) or extensional (instances graphs: G + [15, 16, 17], etc.) data models. Recently so...