1. A method comprising: storing an ontology map comprising link mappings of one or more link types defined by a first ontology to one or more link types defined by a second ontology; wherein the ontology map comprises a mapping from a first object type defined by the first ontology to a second object type defined by the second ontology and a mapping from a third object type defined by the first ontology to a fourth object type defined by the second ontology; wherein the first ontology defines a first link type as including a first direction of relationship between the first object type and the third object type, and the second ontology defines a second link type as including a second direction of relationship between the second object type and the fourth object type; wherein the link mappings comprise an asymmetric mapping from the first link type of the first ontology to the second link type of the second ontology that specifies that the first direction of the first link type is opposite to the second direction of the second link type; receiving a set of one or more database changes that were made using the first ontology and comprising a change involving a first link of the first link type; based at least in part on the asymmetric mapping, incorporating the set of one or more database changes into a set of data that is organized according to the second ontology, at least in part by using the asymmetric mapping to determine a direction of a second link of the second link type; wherein the method is performed by one or more computing devices.