Access Independent Query Definition in IBM DL/I
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
An implementable mapping between DL/I data bases by means of a simple conceptualization of their structure associates together the set of paths defined in various data bases and having a common query structure; that is to say, any one of the set may be used to execute a query defined on any of the others. Membership of this set is both a necessary and a sufficient condition for access equivalence with any other member of the set and allows a query system the widest possible domain of effective paths from which its access optimization routines may select the most efficient. The definition of these domains, each associated with a segment selectable for a query, may efficiently be performed once only, before online query execution.