  We study the problem of continuous object dissemination---given a large
number of users and continuously arriving new objects, deliver an object to all
users who prefer the object. Many real world applications analyze users'
preferences for effective object dissemination. For continuously arriving
objects, timely finding users who prefer a new object is challenging. In this
paper, we consider an append-only table of objects with multiple attributes and
users' preferences on individual attributes are modeled as strict partial
orders. An object is preferred by a user if it belongs to the Pareto frontier
with respect to the user's partial orders. Users' preferences can be similar.
Exploiting shared computation across similar preferences of different users, we
design algorithms to find target users of a new object. In order to find users
of similar preferences, we study the novel problem of clustering users'
preferences that are represented as partial orders. We also present an
approximate solution of the problem of finding target users which is more
efficient than the exact one while ensuring sufficient accuracy. Furthermore,
we extend the algorithms to operate under the semantics of sliding window. We
present the results from comprehensive experiments for evaluating the
efficiency and effectiveness of the proposed techniques.
