Comparisons Involving Index-Names and/or Index Data Items (Relation Condition)

General Rules:

1. Relation tests can be made only between:

   1. Two index-names. The result is the same as if the corresponding occurrence numbers were compared.
   2. An index-name and a numeric data item or numeric literal. The occurrence number that corresponds to the value of the index-name is compared to the data item or literal.
   3. An index data item and an index-name or another index data item. The actual values are compared without conversion.
   4.  An index-name can be compared with an arithmetic expression. The occurrence number that corresponds to the value of the index-name is compared to the computed value of the expression.
   5. The result of the comparison of an index data item with any data item or literal not specified above is undefined.