The type OclSummable defines the sum and zero operations used by the Collection::sum iteration. Only types that provide derived sum and zero implementations may be summed.
conformsTo 
				
					OclAny
				
			
Operations
				
sum(that : OclSelf[?]) : OclSelf[?]
			
Return the sum of self and that.
The sum operation should be associative.
				
zero() : OclSelf[?]
			
Return the ‘zero’ value of self to initialize a summation.
zero().sum(self) = self.