“…Although somehow complex rules can be expressed, using them in the query optimisation becomes too difficult; also the rule maintenance becomes problematical. Therefore the rule representation is limited to using simple rules [8,13,7,3,24,20,10,6,1,25,12,14,18,9,23,2,22]. Assuming a table is R (x, y, z) where x, y and z, are attributes of R. A rule can be formed as x⊕a → y⊗b where a and b are constant values; ⊕ and ⊗ are one of comparison operators ¡, ¡=, ¿, ¿=, =, !=.…”