My question is about the description of general defects (specially loop defects) in the Walker-Wang (WW) model.

Elementary excitations in the WW model can be point particles, loop defects and more general defects (see page 12 of arXiv:1104.2632). It is stated their description is closely related to the boundary condition of 3-manifolds.

From my understanding, a boundary condition is a collection of ribbon ends on the surface boundary Y. One can then define a 1-category A(Y) in which objects are the boundary conditions, morphisms are linear combinations of string-nets in Y x [0,1], between Yx0 and Yx1, and composition is given by 'stacking'. If I am not mistaken, excitations are then associated with the hom spaces of this category.

Does this construction encapsulate all types of higher defects including loop defects? If so, then how can I think of loop defects in this setting?