Hypergraphs and base station location

In cell planning (specifically in base station allocation for wireless networks), a hypergragh H is a set system composed of directed monomial graphs p(x)= x^E in such a way that a central vertex is acheived in each one of them.Where each central vertex represents an irradiating source (M') and hyperedges are arcs in the form of E'=(x,y) directed from x to y. Where E' is a subset of E (edges), and M' is a subset of M (all possible Base Station locations). Note: any number of vertices can belong to E' within the (x,y) boundary.

Can anyone please explain this paragraph specially what we mean by directed monomial graphs p(x)= x^E ??????

Thanks in advance.