3) Controller
Controller is responsible for daily jobs of the node. It
activates some knowledge sources from knowledge source
set and puts them into scheduling queue according to the
information of result status reported by running nodes. It
obtains loads and resources of running nodes to keep node
information table correct. It allocates knowledge sources in
the executable queue to running nodes in terms of proper
algorithm. It manages the whole knowledge source set and is
responsible for migration of knowledge sources to keep
system loading balanced.