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MODEL guidance please

herbert_bernstein (yaya@aip.org)
Sun, 10 Mar 96 06:23:12 EST 

Paula's message says that NMR ensembles of structure are to be handled
by the existing ATOM_SITES_ALT category.  I am trying to design code
for this purpose and would appreciate guidance on what is intended.
The specific test case that keeps tripping me up is as follows:
  Suppose you have 50 models.  Within each model, suppose there
are two regions of microheterogeneity.  Within each region suppose
one variant has 4 residues and the other has 5 (just to make sure
we know how to handle ENTITY_POLY_SEQ).  Now suppose within each
variant within each region there are four disordered atoms, with
2 alternate positions each.
  I have tried dealing with this by structuring
_atom_site.label_alt_id in the form model.variant.altpos, but then
I end up violating the usual rules on sums of occupancies, and, worse,
when I try to generate the ensembles to describe each model, each
variant, and each disordered site, I seem to be getting
combinatorial explosion.
  Guidance please.
P.S.  My apologies for using "model.variant.altpos," since that
effectively overloads a token, just as a return to number(esd)
would, but it does help to clarify the discussion.