User:Physis/Gödel-Herbrand-Kleene equational calculus

Definition

Defined in the follwing way.

The calculus consists of a set (or system) of equations. An equation is of form <term> = <term>, where the left-hand side term may be required to contain a principial letter. Let the set of nonlogical symbols contain the unary f (besides the arithmetical ones 0 and s). This f is just an example of a particular signature, in generally, an arbitrary signature must be considered (which contains the signature of natural numbers at least as an 0 and s).

Syntax

<equation> ::= <lhsterm> = <term>

<lhsterm> ::= 0

<lhsterm> ::= s <term>

<lhsterm> ::= f <term>

<lhsterm> ::= g <term> <term>

<term> ::= <variable>

<term> ::= <lhsterm>

Rules

${\frac {\gamma \in \Gamma }{\Gamma \vdash \gamma }}$

${\frac {\Gamma \vdash \phi }{\Gamma \vdash \phi [x:=\mathbf {m} ]}}$

${\frac {\Gamma \vdash \sigma =\tau ,m\in \mathbb {N} ,n\in \mathbb {N} ,\Gamma \vdash f\mathbf {m} =\mathbf {n} }{\Gamma \vdash \sigma =\tau [f\mathbf {m} \to _{1}\mathbf {n} ]}}$

Expressing power

Equivalent power with the theory of partial recursive functions.

References

• Bezem, Marc (2003). Term Rewriting Systems. Cambridge University Press. ISBN 0521391156. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Monk, J. Donald (1976). Mathematical Logic. Graduate Texts in Mathematics. New York • Heidelberg • Berlin: Springer-Verlag.

External links

• [1]