The Data Integration Service resolves one level of variable values. The Data Integration Service does not resolve variable values that are nested within another workflow parameter or variable.
For example, you create the following workflow variables with these datatypes and initial values:
Variable1 with an integer datatype and an initial value of 4
Variable2 with an integer datatype and an initial value of 3
Variable3 with a string datatype and an initial value of
${var:Variable1} + ${var:Variable2}
When you use Variable3 in an expression or task field, the Data Integration Service does not resolve the nested variables Variable1 and Variable2 to the value of 7. Instead, the Data Integration Service uses the following string value for Variable3: