Transform the query into a query on fragments.
Fragmentation
PROJ1 = SEL(LOC = "New York") PROJ
PROJ2 = SEL(LOC != "New York") PROJ
ASG1 = ASG SEMIJOIN PROJ1 (PNO)
ASG2 = ASG SEMIJOIN PROJ2 (PNO)
EMP1 = SEL(TITLE = "Elect. Eng." OR "Syst. Anal.") EMP
EMP2 = SEL(TITLE = "Mech. Eng." OR "Programmer") EMP
SELECT ENAME, TITLE
FROM ASG, EMP, PROJ
WHERE EMP.ENO = ASG.ENO
AND ASG.PNO = PROJ.PNO
AND BUDGET > 200000
AND (RESP = "Manager" OR RESP = "Consultant")