In the last mads draft we introduced the constraint that an item
(authority, variant, or  related) must have exactly one high-leve
descriptor.That descriptor could be composed of several subordinate
descriptors, but that set of descriptors  must be pre-defined, as for
example, the nameTitle descriptor is composed of  a name descriptor and a
title descriptor. That was the only pre-defined  high-level descriptor with
subordinate descriptors, and we said that  additional such descriptors would
be added if necessary.

 We at LC now believe that this constraint is too restrictive, and that a
mads item should be allowed to include an arbitrary list of descriptors, at
the discretion of the creator of the record.

 For example, one might imagine the following record where the authority has
three descriptors:  <geographic>, <topic>  and <temporal> (and the variant
has  four:  <geographic>, <topic>, <temporal>, and  <topic>):

<geographic>United States </geographic>
<topic>Foreign relations</topic>
<variant type="earlierHeading">
<geographic>United States</geographic>
<topic>Foreign relations</topic>
<temporal>Revolution, 1775-1783</temporal>
<variant type="other">
<geographic>United States</geographic>
<temporal>Revolution, 1775-1783</temporal>

(Not related to the subject at hand but note the value "earlierHeading" of
the type attribute for variant. It's not in the current mads draft but we
propose to add it. This is different than "earlier" which is a value for
related for an earlier name, as opposed to an earlier heading.)

 We think it would not be useful to try to enumerate all of the possible,
meaningful combinations of descriptors. So we propose to remove this
restriction in the next draft (and remove the nameTitle descriptor).