8. A system, comprising at least one processor, for processing queries, and further comprising: a database abstraction model that provides a set of logical fields used to compose an abstract query, wherein each logical field specifies (i) an access method that maps the logical field to data in an underlying physical database; a runtime component, which when executed by the one or more processors is, configured to receive: a physical query having a format that is executable by a query engine to access the underlying physical database; and in response to the physical query, to generate, 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) the 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) a reference to an access method selected from at least two different access method types, wherein each of the different access methods types defines a different manner of exposing the data corresponding to the name of the logical field.
8. A system, comprising at least one processor, for processing queries, and further comprising: a database abstraction model that provides a set of logical fields used to compose an abstract query, wherein each logical field specifies (i) an access method that maps the logical field to data in an underlying physical database; a runtime component, which when executed by the one or more processors is, configured to receive: a physical query having a format that is executable by a query engine to access the underlying physical database; and in response to the physical query, to generate, 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) the 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) a reference to an access method selected from at least two different access method types, wherein each of the different access methods types defines a different manner of exposing the data corresponding to the name of the logical field. 9. The system of claim 8 , wherein the physical query comprises an SQL statement and the underlying physical database comprises a relational database, wherein the relationships between data sources are indicated by a relational schema of the relational database.