Systems and methods to store data obtained from observations and to determine a correspondence of certain data to a particular person. In one approach, a method includes: receiving or making a plurality of observations for a person (e.g., data extracted from e-mails sent to the person); storing the observations in a repository (e.g., a database on a server); and determining whether data in a first observation of the observations corresponds to the person, wherein the determining is based on the plurality of observations.