When a query is to be processed, the node layer requests the
required tuples from the device manager. Then, the query is processed using
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Jinbao Li, Zhipeng Cai, and Jianzhong Li
those tuples and the results are sent to the cluster leader. In addition to its
node processing layer the cluster leader has an active leader processing layer,
which receives tuples from the other members of the cluster. The tuples it
receives are delivered to each query from the FrontEnd that needs the tuples.
The leader layer then processes the queries using the received tuples and sends
the replies to the FrontEnd that initiated the query. When appropriate, tuples
are aggregated before being sent out.
FrontEnd
software running on the sensors. It keeps track of the queries currently running
for the GUIs running on the system and receives messages from nodes
that are cluster leaders. The FrontEnd delivers each tuple to the queries that
require it, does some processing of the tuples, and sends a response to the
GUI that initiated the query. FrontEnd can receive queries from GUI. It can
also send messages to GUI to direct it start up a query. It can also output
tuples to a remote MySQL database.
GUI
The GUI allows users to pose queries either visually or using SQL and
to display query results in tabular format. A map component in GUI allows
users to visualize the topology of the sensors in the network. Users can collect
nodes into clusters, which automatically elect a leader.
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