Extent definitions

ODABA extents are defined as part of a persistent structure. ODABA extents may for hierarchies and can reflect set relations as subset, intersect or union. Extent hierarchies allow also dividing a collection in a distinct and complete set of subclasses.

Structure instances can be stored on a global level in one or more controlled extents. Each structure instance, however, is owned by exactly one extent. Usually, one extent is defined as so-called root extent, which is the owner of all instances. In principle, however, it is possible to define any number of root extents for a persistent structure.