3.1 b-h: Link contents question matrix

The ERB schedule calls for voting on Feb. 26 on these items.

It seems to me that these can sanely only be discussed collectively. 
It is multi-part and multi-dimensional, but none of the parts seem
really orthogonal to any of the others.  If people wish to take up
sub-questions in detail, this is welcome.  I encourage creativity
and discipline in the use of subject lines to enhance the usefulness
of the discussion.  

Dimension 1: Which pieces of information should be specified for
possible inclusion in linking elements?

b. Type
c. Role
d. locator
e. caption
f. behavior
g. locator scheme (e.g. URL, FPI, TEI locator)
h. others [nominations encouraged]

For each of the pieces of information to be included in linking
elements, the following questions apply:

(i)  should it be optional or required?
(ii) should it be associated with links or allowed to vary per locator?
(iii)should it be carried in the GI, in an attribute name, or in an attribute 
     name-value pair?
(iv) should we predefine a set of values?
(v)  if so, should we provide a mechanism for "subclassing"?
(vi) should we allow the use of values other than those predefined or
    subclasses thereof?