US Patent 7505976 Access controller using tree-structured data

Provide access control devices methods and systems that include a data structure which makes the data amount of a database constituting policies as small as possible even if a policy including a number of complicated conditions is set. An access control device of the present invention receives inputs of policies each for controlling access to a part of a data source, and stores these policies. The access control device generates tree-structured data from the stored policies, merges these tree-structured data, and stores the merged tree-structured data. When determining whether or not access should be permitted, the access control device performs determination on the basis of this stored tree-structured data.