1. A computerized method of establishing relationships between one or more entities of a first application and one or more entities of a second application, said computerized method comprising: identifying at least one entity of the second application for establishing a relationship with at least one entity of the first application; receiving, at the first application, metadata from the second application, said metadata including information associated with the identified entity of the second application; and generating, based on the metadata, an expression specifying a relationship between the entity of the first application with the identified entity of the second application.