[Om3] first suggestion

[Michael Kohlhase]

Dear all,

after all the admin and announcements are out of the way, here is the 
first suggestion.

MathML does not have the notion of a role of a symbol, but it does use 
some symbols as both a binding, and application symbol.

An example is the <union> symbol, with role application is the union 
operator we all know and love as in S\cup T

with the role "binder", we can use it as a binding operator \bigcup{i\in 
I}S_i

If we were to rethink the role of a symbol in OM3, we could support this 
behavior as well

I was quite opposed to this dual role behavior of symbols, but my 
colleagues at Linz have me partially convinced.

In the standard we have some complex rules what the roles mean (e.g. 
"constant" means that  the symbol cannot be  used to construct complex 
OM objects).  While "application" means that  it can be used as  the 
head of an application and as standalone object as well.

If we allowed multiple roles, then we could give the function symbols 
the roles "appication" (meaning 'only as the first child of an OMA') and 
"constant" (meaning 'only standalone'), and have a much clearer picture. 
And we could ease alignment for MathML by allowing to keep dual-use 
symbols (these would otherwise have to be duplicated by role).

What do you think?

Michael

-- 
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 Prof. Dr. Michael Kohlhase,       Office: Research 1, Room 62 
 Professor of Computer Science     Campus Ring 12, 
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 Jacobs University Bremen*         tel/fax: +49 421 200-3140/-493140
 m.kohlhase at jacobs-university.de http://kwarc.info/kohlhase 
 skype: m.kohlhase   * International University Bremen until Feb. 2007
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