Query-by-example-operations on hierarchical data bases

Abstract

Query-by-Example is a high level non-procedural data base language which provides the end user with a simplified unified interface for querying, updating, defining, and maintaining, the data base, as well as imbedding various integrity and authority constraints. When querying the data base the user fills in, through a keyboard display, an example of a possible answer in a skeleton of the logical structure of the data base. As demonstrated in previous work, when the data base is relational, skeleton tables are used. In this paper, we show that the Query-by-Example operations are in fact independent of the structure of the data base. In particular, we demonstrate that if the view at the user interface level is hierarchical, the query is again accomplished by filling-in an example of a possible answer, but, in this case, a skeleton of the hierarchy is utilized. It is, also, shown how the user can map a relational view into a hierarchical view and vice versa, formulating queries that involve both views simultaneously. Finally, a linear version of Query-by-Example is made available for situations where a display facility is unavailable.