Normal categories of semigroup of order-preserving transformations on a finite chain

Abstract: K. S. S. Nambooripad intoduced nornal categories to enable to describe the structure of regular semigroups fully. In this paper we describe the ideal categories of the regular semigroup $OX_n,$ of non-invertible order-preserving transformations on a finite chain $X_n={1\leq 2\leq \cdots \leq n }$ which are normal categories. Further it is shown that the principal left ideal category of $OX_n$ as the power set category $P_o(X_n)$ of $OX_n$ and the principal right ideal category as $\prod_o(X_n)$ category of ordered partitions of $X_n$ and described the cone semigroup $T\mathscr L(OX_n)$ and prove that it is isomorphic to $OX_n.$