Collaborative query processing based on

reducts

Example of a non-local query (DS-term)

Database:Flights(airline; departure time; arrival

time;departure airport; arrival airport)

select * from Flightswhere airline = "Delta”departure time = "morning"departure airport = "Charlotte"aircraft = "Boeing"

(a1*c2)+(d2*a2)

(a1*c2)+(a1*b2*a2+d2*a2)

(a1*c2)+(a1*b2+d2)*a2

(g1, a2)

(g1, a2, a1)

(f2, a1*b2+d2)

(f2, a1*b2+d2, a2*d1)

{d,c,e,g}{a,b,c,d,f}={c,d} {a,b}, {a,c}, {b,c} {d,c,e,g}

= q (c, e, f (b(e), c ))

= q (c, e, f (b, c )) =

q = q (c, e, f ) = q

S1

e

cb

fec S1

S1

S2

S2

S3

Tree-resolution for q