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sav08:homework09 [2008/04/24 23:13] vkuncak created |
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- | ====== Homework 09 - DRAFT, Due Wednesday, April 30 ====== | + | ====== Homework 09 - Due Wednesday, April 30 ====== |
===== Problem 1 ===== | ===== Problem 1 ===== | ||
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Prove that the quantifier-free theory of term algebras is convex (See [[Calculus of Computation Textbook]], Section 10.3.1). That is, show that, if $C$ is a conjunction of literals of form $t=t'$ and $t\neq t'$ where $t,t'$ are terms in some language (containing variables), and if formula | Prove that the quantifier-free theory of term algebras is convex (See [[Calculus of Computation Textbook]], Section 10.3.1). That is, show that, if $C$ is a conjunction of literals of form $t=t'$ and $t\neq t'$ where $t,t'$ are terms in some language (containing variables), and if formula | ||
\[ | \[ | ||
- | C \rightarrow \bigvee_{i=1} t_i=t'_i | + | C \rightarrow \bigvee_{i=1}^n t_i=t'_i |
\] | \] | ||
- | is valid in the Herbrand interpretation, then for some $i$ | + | is valid (holds for all values of variables) in the Herbrand interpretation (where elements are ground terms and $\alpha(f)(t_1,\ldots,t_n)=f(t_1,\ldots,t_n)$), then for some $i$ |
\[ | \[ | ||
C \rightarrow t_i=t'_i | C \rightarrow t_i=t'_i | ||
\] | \] | ||
- | holds. | + | holds for all values of variables in the Herbrand interpretation. |
+ | |||
+ | If you use in your solution any theorem about term algebras that we did not prove in the class, you need to prove the theorem as well. | ||