1. A security document database, the database storing security document data including, for each of a number of security documents: identity data, the identity data being at least partially indicative of an identity of the security document; attribute data, the attribute data being at least partially indicative of one or more attributes of the security document; wherein, in use, the security document database allows a computer system to: receive, from a sensing device, indicating data at least partially indicative of at least one of: the identity; and one or more attributes; use the received indicating data and the security document data to perform an action associated with the security document.