In this paper a 1 inkdot two way alternating pushdown automaton (2apda) is introduced which is a two way alternating pushdown automaton (2apda) with the additional power of marking at most 1 tape cell on the input (with an inkdot) once.

• 该文引入 1墨水点 2方向交替式下推自动机 ,它是 1个具有额外能力的 2方向交替式下推自动机 ,能够用 1个墨水点在输入带上标记出最多 1个单元格。