TSA

Tree stack automata

a tree stack is a tree with a designated position in it. The root of the tree serves as bottom-most symbol and the leaves are top-most symbols. We allow the stack pointer to move downward (i.e. to the parent) and upward (i.e. to any child). We may write at any position except for the root. We may also push a symbol to any vacant child position of the current node.

— An automata characterisation for multiple context-free languages, 2018