FM+SGML: Ambiguous EDD General Rules - Why?

[eric.dunn@xxxxxxxxxxxxxxxxxxxxxxxxxxx]

Why on earth are the following rules ambiguous? The first one particularily
looks pretty straight forward, but FM+SGML gives me a report that they're all
ambiguous. (Rules formatted as report output with added ^'s)

A, B?, C, D, ^C?, (H| J)*, B*, ^C?

A, ((B, C, D, C?) | (C, D, ^C?, E?, F?, G?, (H| I| J| B)*, ^C?))

A, ((B, C, D, C?) | (C, D, ^C?, E?, G?, (H| J| I)*, B*, ^C?))

A, ((B, C, D, C?) | (C, D, ^C?, E?, F?, G?, (H| I| J| B)*, ^C?))

Tried to figure out why they were ambiguous but I couldn't. I did however take a
stab at it by figuring that breaking up the rule further might help. In other
words, fragment them to separate the indicated ambiguous elements ( ^ ).
Changing the rules to the following solved the problem. (added parentheses
denoted by _(_ and _)_ )

_(_ A, B?, C, D, C? _)_ , _(_ (H| J)*, B*, C? _)_

A, ((B, C, D, C?) | ( _(_ C, D, C? _)_ , _(_ E?, F?, G?, (H| I| J| B)*, C? _)_
))

A, ((B, C, D, C?) | ( _(_ C, D, C? _)_ , _(_ E?, G?, (H| J| I)*, B*, C? _)_ ))

A, ((B, C, D, C?) | ( _(_ C, D, C? _)_ , _(_ E?, F?, G?, (H| I| J| B)*, C? _)_
))

While I nolonger need to stress out trying to find a solution, it wouldbe nice
to know why the problem existed in the first place.

Eric L. Dunn



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