1. A computer-implemented method comprising: providing in a database layer, a database engine and a database comprising data organized according to a relational model; providing in an application layer, an entity relationship data model and a query engine in communication with the database engine; causing the database engine to receive from the query engine, a query in a database language extended to include an entity type and an association, the query further comprising a path expression specifying a relationship between a specified entity and an associated entity; causing the database engine to return to the query engine, a query result comprising data of the associated entity fetched along the path expression.