Be more precise about the values 'text', 'char' and 'line' in style:vertical-rel

This issue is about the attribute 20.398 style:vertical-rel in ODF1.3 part3, especially about the attribute values 'text', 'char' and 'line'. This attribute describes the reference area for the attribute style:vertical-pos.

Currently the text is:
char: vertical position of frame positioned relative to a character.
line: vertical position of frame positioned relative to a line.
text: vertical position of frame positioned relative to text.

It is not clear, which area is covered by 'character', 'line' or 'text'.

I have no proposal yet, because I don't know, how these attribute values are actually used in applications.

When the meaning is clear to us, it would be good to illustrate the areas.