1. A method for storing data in a computer data repository, comprising the steps of: storing in a first table data identifying at least a first item and at least first and second sub-items associated with said first item; storing in a second table at least a first and a second attribute identification associated with said first item, said first and second attribute identification each identifying a property of said first item; and storing attribute values for said first attribute identification, said attribute values associated with said first and second sub-items, respectively.