[tei-council] modifying @rend

[Syd Bauman]

CW> How to I express this wish in ODD?

SR> <classSpec ident="att.global" mode="change">
SR>   <attList>
SR>     <attDef ident="rend" mode="change">
        <!--                 ^^^^^^^^^^^^^ -->
SR>        <datatype>
SR>            <rng:text/>
SR>         </datatype>
SR>     </attDef>
SR>   </attList>
SR> </classSpec>

Why is the indicated mode= required? I've been tripped up on this
several times, because I thought that mode= was inherited.

If I go back and read TD carefully, will I discover this is clearly
documented, and I was just too eager to dive in before RTFMing?