Proposed rewrite of Appendix G

Further to previous correspondence about p:import and step-name
conflict detection, here's a proposed rewrite for the appendix which
gives an informal algorithm for checking for problems/handling imports
in general.

Note that unlike the previous one, it's essentially specified
bottom-up, in terms of _exports_, because when I tried to implement it
that's what worked most easily (I wrote a Scheme implementation of the
algorithm before I defined it).

I'm particularly interested on feedback on the form of the exposition:
rather then do it in pseudo-code as the original has, with lots of
variables and processes which all take two arguments and return two
values, I've tried to do it at a more abstract level.

ht

-- 
       Henry S. Thompson, School of Informatics, University of Edinburgh
                         Half-time member of W3C Team
      10 Crichton Street, Edinburgh EH8 9AB, SCOTLAND -- (44) 131 650-4440
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                       URL: http://www.ltg.ed.ac.uk/~ht/
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