1. For repeatable *fields* referenced by *index* and *indicators* the *fields* MUST first be referenced by *index*. *Indicators* work like a filter on the referenced *fields* as a second order.

1. The *postion* character ```#``` is always a reference to the last character in the *data content*.

2. For character range, if the *positive integer* used for the character starting position is greater than the *positive integer* used for the character ending position, the current spec MUST NOT reference any data.

3. For character range, if the character ```#``` is used for the character starting position, the character indices MUST be interpreted backwards (like character ending position ```0``` for the last character, ```1``` for the last but one character, ```2``` for the last but two characters etc.).