1. A computer-implemented method of providing access to data having a particular schema, comprising: in response to receiving an abstract query, accessing a data abstraction model which models the data having the particular schema and exposes the data to users in a manner that allows the users to compose queries on the basis of the data abstraction model without knowledge or regard for the particular schema; wherein the model comprises a plurality of logical field definitions, each of the definitions comprising a logical field name, at least one location attribute identifying a location of physical data corresponding to the logical field name, and a reference to an access method invoked to access the physical data in response to receiving the abstract query containing the logical field name; wherein at least one of the logical field names is different from a physical field name of the corresponding physical data as defined by the schema.