1. A method of providing fee-based access to data, comprising: providing an abstract model for logically defining abstract operations to access the data, the abstract model comprising: (i) a plurality of logical fields; (ii) a mapping rule for each of the plurality of logical fields, which map the plurality of logical fields to physical entities of the data; and (iii) a fee schedule for each of the plurality of logical fields, wherein each fee schedule for a given logical field defines a fee to be charged when the given logical field is involved in an abstract operation to access a physical entity corresponding to the given logical field.