ext-rep file naming

[Leonard Soicher]

Dear All,

This posting is to keep everyone up-to-date on the topic of file naming
for lists of block designs in external representation format (file names
such as  v6-b8-k3.icgsa.xml ).

First, it has been agreed that, by default, the files will contain *only*
binary, connected block designs, so by default the special indicator
`a' means the file contains all binary connected block designs up
to isomorphism with the parameters specified by the file name. It is
perfectly possible for a file with special indicator `a' to contain no
block design, to make the assertion that there is no binary connected
block design with the parameters specified by the file name (in this 
case each (other) content indicator may or may not be present).

It has also been decided that, for now at least, not to use the
`r' content indicator. This is because some designs in a list may
be resolvable and have a <resolutions> subtree, and some may not be
resovable.  At present, non-resolvability is communicated only in the
<indicators> subtree; it is not presently allowed to have an empty list
of resolutions in the <resolutions> subtree.

Regards,  Leonard