Guidelines for defining an implicit unordered group that has no delimiter
- The type of a component cannot be a binary item whose length is not fixed.
- The type of a component must be content-distinguishable from the type of each other component.
- If the type of a component is unbound, the type must be ending-distinguishable from the type of each other component.
- If the maximum range is greater than one and the type is unbound, the type must be ending-distinguishable from itself.