In this section we consider the kinds of data that might be propagated, i.e., guessed at or estimated, in filling out the individual identifiers of a genealogical record linkage entity. In some cases it is necessary to undo the effects of any propagation that might have been performed by a researcher to get at the data that record linkage must take into consideration. The date of an event is one of the simplest data structures, yet its propagation is the most involved and precise. Next in complexity is the locality of an event. The simplest, and least amenable to propagation is the name of the individual. The semantic base for personal names are the individuals, which are identified by vital events having dates and localities. The vital events of an individual which may be propagated are birth, marriage, and sometimes death. As it is possible to propagate a death from a probate or burial record, it is also possible to propagate the other way around: a possible probate, or burial from a death. The record linkage algorithm must take into account all these possibilities when weighting the relative importance of the data in the fields of the records to be linked.
Here we consider only the most basic rules. The examples we give all relate data identifying the principal of an event document (P1) to a person whose identifying information is being generated (P2). All data propagation rules may require the following four elements: 1) the relationship of P1 to P2, 2) the marital status of P1 (conditional on value of relationship), 3) the sex of P1, 4) the precision of the identifiers for P1 and P2. In addition to these four basic elements, there are at least two others that are important to consider when devising a date propagation rule: 5) conditions on the age of P1, 6) parameters needed for calculations. Propagation rules for personal names also require specification of the four basic parameters. In this case precision may be indicated possibly by the pre-positive title produced.