Using the Propagation Routines - trillium_discovery - trillium_quality - 17.2

The propagation routines are used with a regular comparison routine to prevent transitivity from occurring during the Relationship Linker or Reference Matcher process. Transitivity happens when two records match indirectly through a third record. For example, if record A matches B, and A matches C, B can match C, which generally would not be desirable.

When the propagation routine is invoked, if records A and B match and A has a blank (or zero) in one field and B has a value, the value is "propagated" in memory until record A has gone through all the records in the match window. Record A obtains a temporary copy of B’s value for future comparisons, which causes the A - to -C match to fail, thus prevents the B-to-C match (transitivity).

The following table lists the valid propagation routines:

Example

In the example below, when Record A is compared to Record B, the blank apartment matches to an apartment number (Apt 1), so Record A and Record B match. Then Record A is compared to Record C and they also match. Because A matches B and A matches C, B matches C by transitivity, which is not correct.

To prevent transitivity, you specify the nonblank propagation routine for the APTNO comparison routine in the Field List Editor.

When the Relationship Linker runs next time, Record A obtains a temporary copy of B’s apartment number for further comparisons. When Record A is compared to Record C, they do not match, thus Record B does not match Record C either.