Truncation of functional relations in the XXZ model

This is the abstract of the revised paper. The integrable XXZ model with a special open boundary condition is considered. We study Sklyanin transfer matrices after quantum group reduction in roots of unity. In this case Sklyanin transfer matrices satisfy a closed system of truncated functional equations. The algebraic reason for the truncation is found.The important role in proving of the result is performed by Zamolodchikov algebra introduced in the paper.