The structure of two generalization of the symmetric inverse semigroups
  We introduce two generalisations of the full symmetric inverse semigroup ${\mathcal{I}}_X$ and its dual semigroup ${\mathcal{I}^{\ast}}_X$ -- inverse semigroups ${\mathcal{PI}^{\ast}}_X$ and ${\overline{\mathcal{PI}^{\ast}}}_X$. Both of them have the same carrier and contain $\IS_X$. Binary operations on ${\mathcal{PI}^{\ast}}_X$ and ${\overline{\mathcal{PI}^{\ast}}}_X$ are reminiscent of the multiplication in ${\mathcal{I}}_X$. We use a convenient geometric way to realise elements from these two semigroups. This enables us to study efficiently their inner properties and to compare them with the corresponding properties of $\IS_X$ and ${\mathcal{I}^{\ast}}_X$. 
Ganna Kudryavtseva and Victor Maltcev