Abstract: A set of subscriptions are provided, where one or more subscriptions each comprises a tree pattern, and a tree pattern comprises one or more interconnected nodes having a hierarchy and adapted to specify content and structure of information. The set of subscriptions is used to select information for dissemination to users. Generally, the one or more subscriptions having the tree pattern describe information the users are interested in receiving. Techniques are presented for determining an aggregation from the subscriptions, where the aggregation comprises a set of aggregate patterns. The set of subscriptions may comprise a number of tree patterns, and the aggregate patterns generally also comprise tree patterns comprising one or more interconnected nodes having a hierarchy and adapted to specify content and structure of information. The set of aggregation patterns is smaller than the set of subscriptions and can be made to fit any space constraint.