1. 1-1 CMPE 259 Sensor Networks Katia Obraczka Winter 2005 Storage and Querying

2. 1-2 Overview

3. 1-3 Overview r Sensors sense/generate data. r Users/applications interested in data. r Require an infrastructure for data access and storage. r Common user operations are: m Queries (monitoring). m Actuate and control.

4. 1-4 Types of queries r Historical: m What is the average rainfall over past 2 days? r Current: m What is the current temperate in Rm# 226? r Long running: m Temperature in rm# 226 over the next 4 hours every 30 seconds.

5. 1-5 Issues r How to identify relevant sensors? r Computation vs. communication tradeoff. m Where to process query? Inside the sensor network (route query). At centralized location (route data). –Large amounts of data transfer: efficiency? m How to process query?

6. 1-6 DataSpace: Querying and Monitoring Deeply Networked Collections in Physical Space T. Imielinski and S. Goel, Rutgers University r Billions of objects populate space. r Each produces and locally stores data. r Location aware. r Can be selectively monitored, queried and controlled.  Physical world enhanced with data.

7. 1-7 Characteristics r Dataspace m Data lives on the object m Users access not only “local” information but can navigate entire dataspace m Spatial world divided in 3-D datacubes CS Bldg., street, block etc m Communication, messaging and computation techniques for querying and monitoring required

8. 1-8 Querying and monitoring r Queries are spatially driven. r Steps: m Identify relevant datacubes. m Identify relevant nodes (dataflocks). Datacube directory service. m Aggregation for queries on several datacubes. E.g.,information about Manhattan taxi cabs

9. 1-9 Architecting DataSpace r Querying and monitoring. m Multicast mechanisms. (attribute, value) pair mapped to a multicast address. m Group membership based on: Physical location. Attribute (temperature, #vehicles, etc.). m Mapping (attribute, value) to multicast address. E.g., using hash tables. m Condition on the index attribute of query mapped to multicast address. Query reaches all objects satisfying condition on index attribute. Objects perform check for remaining conditions and respond or not.

10. 1-10 Where to provide functionality? r Network versus application layer.

11. 1-11 Network as DataSpace engine Space Handle identifies datacube. Subject Handles are (attribute, value) pairs such that attribute is indexed. DataSpace address Based on location of datacube Based on relevant attribute

12. 1-12 Using geographic routing infrastruture r Route message based on physical location. m Use GPS coordinates for location. r Once query reaches a region use mutlicast.