Hi, good day to everyone , if for example, from literature, I know my protein-protein interaction is rigid body interaction, in HADDOCK, during the “input parameter”, is it right if i set the semi-flexible region as rigid?
There is nothing like a rigid-body interaction.
When in the field we speak of rigid-body interaction we mean there are no conformational changes large than 1A backbone RMSD.
There will always be a bit of small conformational changes. For sure of the side-chains.
So better to leave the flexibility options to their default 
Noted with thanks!! Much appreciated!