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Chapter 6. Using subsets of entity sets

6.10 - Summary

Subsets of entity sets, or selectors are fundamental for the efficient manipulation of the ER data of ADAMO, most notably for navigating from one ESet to another via defined relationships. An ESet may have as many defined selectors as needed but their management is the responsibility of the programmer. The demonstrative program subsets illustrates the basic use of selectors and some of the TAP routines that this may be done with. The concepts introduced in this chapter are:

Selector

An ordered list of the IDs of a subset of rows of a table. A selector may not contain duplicate IDs. A given table may have as many selectors as needed.

Selection

The insertion, into an already existent selector, of the IDs of those rows of a table for which a particular attribute value lies in a specified range.

Navigation

The operation that starts from one or more entities in an ESet and finds related entities in another ESet.

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BR and MR - CERN PTG - ADAMO Users Guide for Version 3.3 - 11 Oct 93