Making purchase decisions

Apparatus according to an exemplary embodiment of the present invention comprises a contract repository ( 200 ) in which details of each of a plurality of contracts established with a supplier of a good or service is stored. Similarly, each of a plurality of purchase orders ( 30 ) submitted by one or more buyers are stored in a purchase order repository 300 . A subsystem ( 1 ) for linking purchase orders ( 30 ) to contracts ( 20 ) and for aggregating information is provided. The subsystem ( 1 ) employs a linking table ( 10 ) for recording links between contracts ( 20 ) and purchase orders ( 30 ). The linking table ( 10 ) in an exemplary embodiment of the present invention includes a column ( 101 ) for recording contract identifiers ( 201 ) in respect of contracts ( 20 ) used to realise purchase orders ( 30 ) a column ( 102 ) for recording in respect of each contract identifier ( 201 ) a list of purchase order identifiers denoting purchase orders realised using that particular contract, and a table ( 103 ) of aggregate attributes in respect of all realised purchase orders. In a described example, the table ( 103 ) of aggregate attributes includes the total quantity ( 501 ) of goods purchased using each contract, and the current discount level ( 502 ) in respect of each contract. At any time, when a link between a contract identifier and a purchase order identifier is generated, the table ( 103 ) of aggregated attributes is also updated. Thus, the aggregated quantity ( 501 ) (which comprises the total quantity of goods purchased using a particular contract) is updated to reflect the additional quantity of goods purchased in respect of the contract. This value ( 501 ) is then used to determine the current discount level ( 502 ) which applies to that contract.