Often a particular resource is a collection of documents
of a single kind. Normally a document records an event that involves individuals. Sometimes a
whole collection, such as the ancestral file (AF) is lineage linked. Such a collection usually has
individuals as separate records and uses the other features of events (dates, places) to identify them.
If we are involved in individual linkage, it is necessary to specify whether the record that the
individuals are contained in are 1) event documents or 2) family structures. These are the two
common contexts of an individual — its so-called merotype. In either case there are transformations
required to fill out the individual or family linkage record. One important kind of transformation
relates the class of the linkage entity across records. These are the entity class transformations.
They specify to the record linkage system to link the father in one family to a male child in another,
for example, or the husband in a census schedule to the groom in a marriage return.
