Executing In-network Queries Using SNEE - Advances in Databases - page 137

downstairs(id:int, time:int, light:int) upstairs(id:int, time:int, light:int)

building(id:int, time:int, light:int)

Fig. 1. Network assumed and sources for each stream

SELECT RSTREAM id, light
FROM building[NOW];
(a) All light readings

SELECT RSTREAM avg(light)
FROM building[NOW];
(b) Average light readings

SELECT RSTREAM u.time, u.light, d.light
FROM upstairs[NOW] u, downstairs[NOW] d
WHERE u.light > d.light;
(c) Correlating Light Readings with Filtering Condition

Fig. 2. Example SNEEql Queries

"

2

1

3

Fig. 3. SNEE components

Fig. 3 presents the interactions between components of the system. The Sen-
sor Network Connectivity Bridge is responsible for interfacing with the WSN.
On WSN nodes, a boot loader is used to switch between 3 program images in
flash memory, depicted in Fig. 4. This is necessary due to the limited size of
the program memory. Images in slots 1 and 2 are preinstalled prior to WSN