1. A method of generating an abstract query from a physical query, comprising: receiving, from a requesting entity, a physical query composed in a query language used to query a physical database; generating, from the physical query, an intermediate representation of the physical query that indicates (i) data sources within the physical database containing data queried by the physical query, (ii) conditions specified by the physical query on the data queried and (iii) relationships between the data sources queried by the physical query; and generating, from the intermediate representation, an abstract query composed from a plurality of logical fields, wherein each logical field specifies (i) a name used to identify the logical field, and (ii) an access method that maps the logical field to data in the physical database.