The main purpose of this paper is to propose a scheme of a proof of the nonsimpleness of the group

(

,

) of area preserving homeomorphisms of the 2-disc

. We first establish the existence of Alexander isotopy in the category of Hamiltonian homeomorphisms. This reduces the question of extendability of the well-known Calabi homomorphism Cal :

(

,

)

to a homomorphism

: Hameo(

,

)

to that of the vanishing of the basic phase function

, a Floer theoretic graph selector constructed in [9], that is associated to the graph of the topological Hamiltonian loop and its normalized Hamiltonian

on

that is obtained via the natural embedding

. Here Hameo(

,

) is the group of Hamiltonian homeomorphisms introduced by

and the author [18]. We then provide an evidence of this vanishing conjecture by proving the conjecture for the special class of weakly graphical topological Hamiltonian loops on

via a study of the associated Hamiton-Jacobi equation.