 The grounded extension of an argument structure is the least fixed point of its characteristic function. An extension \(S\) is complete if it contains every argument that is admissible with respect to \(S\). The grounded extension is the minimal complete extension of a structure. If a structure is well-founded (with no infinite regress of attack relations, then the structure has a unique complete extension that is grounded, preferred, and stable (Dung 1995, 331).