1. A method for providing access to data in an environment of multiple data repositories, comprising: providing, for a requesting entity, a data abstraction model comprising a plurality of logical fields for composing abstract queries; and for each of the plurality of logical fields, providing an access method which specifies at least a method for accessing the data, wherein at least one logical field provides query optimization data for optimizing at least one of an abstract query composed using the logical fields of the data abstraction model and a corresponding resolved query contribution generated from the at least on logical field.