Published online by Cambridge University Press: 10 September 2015
We propose the new concept of Krivine ordered combinatory algebra (  $\mathcal{^KOCA}$ ) as foundation for the categorical study of Krivine's classical realizability, as initiated by Streicher (2013).
 $\mathcal{^KOCA}$ ) as foundation for the categorical study of Krivine's classical realizability, as initiated by Streicher (2013).
We show that   $\mathcal{^KOCA}$ 's are equivalent to Streicher's abstract Krivine structures for the purpose of modeling higher-order logic, in the precise sense that they give rise to the same class of triposes. The difference between the two representations is that the elements of a
 $\mathcal{^KOCA}$ 's are equivalent to Streicher's abstract Krivine structures for the purpose of modeling higher-order logic, in the precise sense that they give rise to the same class of triposes. The difference between the two representations is that the elements of a   $\mathcal{^KOCA}$  play both the role of truth values and realizers, whereas truth values are sets of realizers in
 $\mathcal{^KOCA}$  play both the role of truth values and realizers, whereas truth values are sets of realizers in   $\mathcal{AKS}$ s.
 $\mathcal{AKS}$ s.
To conclude, we give a direct presentation of the realizability interpretation of a higher order language in a   $\mathcal{^KOCA}$ , which showcases the dual role that is played by the elements of the
 $\mathcal{^KOCA}$ , which showcases the dual role that is played by the elements of the   $\mathcal{^KOCA}$ .
 $\mathcal{^KOCA}$ .
This work was partially supported by ANII (Ur), CSIC (Ur), IFUM (Fr/Ur), ANR (Fr).
 $\mathbb R$
                  
               , Logical methods in computer science, vol 7, (3: 02), pp 1–47.Google Scholar
                     $\mathbb R$
                  
               , Logical methods in computer science, vol 7, (3: 02), pp 1–47.Google Scholar $\mathbb N$
                  
               . http://www.pps.jussieu.fr/~krivine/Ultrafiltre.pdf.Google Scholar
                     $\mathbb N$
                  
               . http://www.pps.jussieu.fr/~krivine/Ultrafiltre.pdf.Google Scholar