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Query Processing over a Sensor Network Cornell University Johannes Gehrke Philippe Bonnet Overview Frontend Database Server Sensor.com WINS NG Architecture Problems • Data Model: How to represent devices in a uniform way so that queries can be asked to access them? • Architecture: How to connect the database server and the devices? • Query Execution: Can the traditional query execution techniques be applied in a device database system? • Query Optimization: Are traditional cost based optimizer well suited for device database systems? Problems • Data Model: How to represent devices in a uniform way so that queries can be asked to access them? • Architecture: How to connect the database server and the devices? • Query Execution: Can the traditional query execution techniques be applied in a device database system? • Query Optimization: Are traditional cost based optimizer well suited for device database systems? Problems • Data Model: How to represent devices in a uniform way so that queries can be asked to access them? • Architecture: How to connect the database server and the devices? • Query Execution: Can the traditional query execution techniques be applied in a device database system? • Query Optimization: Are traditional cost based optimizer well suited for device database systems? Problems • Data Model: How to represent devices in a uniform way so that queries can be asked to access them? • Architecture: How to connect the database server and the devices? • Query Execution: Can the traditional query execution techniques be applied in a device database system? • Query Optimization: Are traditional cost based optimizer well suited for device database systems? Data Model • Abstract Data Type (ADT) : class of devices and their methods ex: Infrared Detector : IR IR.detectTrackedVehicle() IR.signature() IR.latitude() IR.powerStatus() IR.detectPersonel() IR.longitude() IR.TurnDown() IR.TurnOn() ex: Camera Camera.orientateTowards(int X, int Y) Camera.latitude() Camera.longitude() • Relation : collection of objects of the same class Declarative Queries Monitoring Queries SELECT R.IR.latitude(), R.IR.longitude() FROM InfraRedDetectors R WHERE R.IR.detectTrackedVehicle(); SELECT FROM WHERE AND AND R.IR InfraRedDetectors R, Positions P $near(R.IR.latitude(), R.IR.longitude(), P.latitude, P.longitude) P.name = “Marina Del Rey Hotel” R.IR.detectPersonel(); Declarative Queries Control Queries SELECT R.IR.turnDown() FROM InfraRedDetectors R WHERE R.IR.latitude() < 100; SELECT C.Camera.orientateTowards(X,Y) FROM Camera C, InfraredDetectors R WHERE $near(R.IR.latitude(), R.IR.longitude(), C.Camera.latitude(), C.Camera.longitude()) AND R.IR.detectTrackedVehicle(); Architecture Sensor Network Graphical User Interface SQL query Proxy Server Proxy Predator Proxy Server • Proxy on each node • Proxy Server needs to address groups of proxies: • at least by class of device • possibly more expressive predicates Proxy Query Execution • Step 1 – Query Processing on the database server (Database Server currently implemented Proxies on Windows CE devices - 01/2000) – Performance Evaluation • Step 2 – Distribution of Query Fragments to the proxy servers and proxies (01/2001) Query Optimization • Relies on meta-information describing the sensor network: – categories of devices, methods supported on each device, statistics concerning the usage of devices, distribution criterion, ... • Initial Optimizer: 01/2000 • Server-based Optimizer: 09/2000 • Distributed Optimizer:09/2001 Conclusion • Today – Prototype based on Predator data model, architecture (proxy servers and proxies in Java), query execution, draft query optimization. • Period 2: – Proxies on Win CE+WINS NG – Server-based Optimizer.