from the following description each business model object has a partner in hew query layer 110 i e a relationship exists between a table and an entity the query subjects also hold the metadata representing the business concept query subjects are collections of attributes query items within the query layer 110 contain expressions related to columns of tables in the underlying database a query item is usually directly related to a single column of the underlying data sources 100 for example the query subject u201c customer u201d could have query items u201c customer name u201d u201c customer address u201d and the like in the simplest case all the query its of a query subject in the query layer 110 are related one to one to the columns of a single table in the underlying data sources 100 however the relationship is not always a one to one relationship also a query item may be expressed as a calculation based on other query items and constants and columns for example a query item may be a summary of data in other query items e g a total amount of all the orders placed by customer embodiments of the present invention thus provide a query layer that describes for relevant data how th data is to be retrieved or imported from the data.