requete prof

r1=selection (avion / cap < 350)
r2=projection (r1, numav, nomav)
r3=selection (avion / loc = 'nice')
r4=projection (r3/numav, nomav)
r5=union (r2, r4)

requete fireboot 

r1=selection (avion/loc=nice)
r2=selection (avion / cap < 350)
r3=union (r1, r2)
r4=projection (r3/ numav, nomav)