1. A method for automatically maintaining identity relationships, the method comprising: providing one or more identity relationship entries that map a source business object having a unique source key in a source enterprise information system (EIS) to a destination business object having a unique destination key in a destination EIS that is separate from the source EIS; detecting a change in the source business object in the source EIS, wherein the change is one of a deletion, a creation, and an update; searching for a target identity relationship in response to detecting the change in the source business object, wherein the target identity relationship is an identity relationship entry comprising the unique source key of the source business object and that relates the source business object to the destination business object; accessing the target identity relationship and updating the target identity relationship in response to finding the target identity relationship; searching for one or more affected identity relationships that are inconsistent as a result of the change in the source EIS, that are hierarchically related to the target identity relationship, and that comprise at least one non-unique key; modifying the one or more affected identity relationships to make the one or more affected identity relationships consistent with the target identity relationship and the source business object in the source EIS in response to finding the one or more affected identity relationships; constructing a business object comprising changes made to the one or more affected identity relationships and the one or more affected target identity relationships; and propagating the business object comprising changes to the destination EIS.