[ubl-cmsc] Context Rule Syntax

[Matthew Gertner <matthew.gertner@schemantix.com>]

7) Syntax of the context rules in general. Assuming that we decide to use a
canonical syntax language (probably XSD), should we align the names of the
context tags so they match the tags in the schema language? Can we handle
all of the various constructs (global types, local types, local elements,
etc.) that are retained by the Naming and Design subcommittee? Are any of
the constructs redundant (e.g. what is the different between "CreateElement"
and an "Add" tag containing and "Element" tag)?