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\noindent
{\bf Intuitionistic Logic (and Planar Heyting Algebras) for Children}

\noindent
Eduardo Ochs - UFF (Rio das Ostras)

\bigskip

In this talk we will see a way to interpret Intuitionistic Logic {\sl
visually}.

One great way to make the expression for children'' precise in
mathematical titles is to define children'' as people without
mathematical maturity'', in the sense that they are not able to
understand structures that are too abstract straight away --- they
need particular cases first.

The structures in which we can interpret operations like and', or'
and implies' and they obey the rules of intuitionistic logic are
called Heyting Algebras. It turns out that finite, planar Heyting
Algebras (ZHAs'') can be drawn as subsets of rectangles, and we will
see how the operations and', or' and implies' can be calculated
visually on them, and why they have to behave in that way. We will
also see how ZHAs can be a tool for understanding Heyting Algebras in
general and several other related concepts, like deduction trees,
simply typed lambda-calculus, and categories.

(Note: this material has been tested on real children --- young
Computer Science students! --- and they liked it a lot)

\bigskip