Let suppose we say that there is a document D and a List of Sensitive Terms S. all NPs are belongs to D. Now IF are those NPs that belongs to S.
(1) IF = All NPs that belongs S.
Now Let suppose we have list A and B. Where A contains Identifiers and B contain medical finding.
All those NPs that is in A are I and All those NPs that is in B are F.
(2) I = { i E D | i E {a E A }}
(3) F = {f E D | f E {b E B}}
So implies that
(4) IF = I = { i E D | i E {a E A }} | F = {f E D | f E {b E B}}
or
(5) IF = I + F