Table 1. Types and numbers of intermediate nodes that were used in complex mappings in the urology project.

Node type	Times used	Description
ADD	9	Adds the numeric values of both operands
EQUALS	2	Returns ‘TRUE’ if operand 1 = operand 2
GREATER	2	Returns ‘TRUE’ if operand 1 > operand 2
GREATERVT	32	Returns ‘TRUE’ if operand 1 > operand 2, operand 1 can be NULL
EXISTS	26	Returns ‘TRUE’ if operands 1 and 2 exist (with operand 1 = operand 2)
NOTEXISTS	8	Returns ‘TRUE’ if operand 1 does not exist and operand 2 exists (see Table G in S1 File for detailed explanation why operand 2 is necessary)
IF	64	Returns the value from operand 2 if operand 1 has the value ‘TRUE’