The visual query language CQL for transitive and relational computation

Classification query language (CQL) is a high-level visual query language w ith a great expressive power. In CQL the processing of ordinary relations a nd classifications based on transitive relationships is integrated seamless ly. Relations and classifications are represented in the visual interface i n a uniform way through relation and classification skeletons. All query fo rmulation in CQL is QBE-like - based on the intuitive way of filling consta nts and sample values into the skeletons. In order to guarantee great expre ssive power, relational and classification expressions can be nested freely with each other at unlimited nesting levels. Recursive definition of trans itive processing is totally hidden from the users. The query interface and its implementation are described briefly. (C) 2000 Elsevier Science B.V. Al l rights reserved.