Understanding character restriction ordering

When input data is assigned to an item (A) that has Exclude character restrictions defined and item A is mapped to an item (B) on output, where item B also has Exclude character restrictions defined, the following process occurs:

• The input data is first validated for item A according to the rules specified in "Validation of Input Data" , and the internal data is constructed.
• The internal data is passed to item B on output and the process described in "Construction of Output Data" takes place, producing the final output data.