ConnectivitySet question

[DanielVandH]

For the ConnectivitySet,

"""
    ConnectivitySet(E_uni, con_E2F, con_E2E, F,  con_F2E, con_F2F, con_V2E, con_V2F, con_V2V, con_V2V_f, con_F2F_v)

# Description 

A struct featuring the connectivity data for a mesh.   
"""
struct ConnectivitySet
    edge_vertex::Vector{LineFace{Int}}
    edge_face::Vector{Vector{Int}}
    edge_edge::Vector{Vector{Int}}
    face_vertex#::Vector{Vector{Int}} # Could be triangle/quad etc
    face_edge::Vector{Vector{Int}}        
    face_face::Vector{Vector{Int}}
    vertex_edge::Vector{Vector{Int}}
    vertex_face::Vector{Vector{Int}}        
    vertex_vertex::Vector{Vector{Int}}
    vertex_vertex_f::Vector{Vector{Int}}
    face_face_v::Vector{Vector{Int}}
    ConnectivitySet(E_uni, con_E2F, con_E2E, F,  con_F2E, con_F2F, con_V2E, con_V2F, con_V2V, con_V2V_f, con_F2F_v) = new(E_uni, con_E2F, con_E2E, F,  con_F2E, con_F2F, con_V2E, con_V2F, con_V2V, con_V2V_f, con_F2F_v) 
end

• What are the precise definitions of these fields? For example, is edge_vertex a set of all edges, or is there a specific meaning for edge_vertex[i]? I thought it would be a vector of all adjoining vertices but that would Vector{LineFace{Int}} I thought, similar for edge_face being a Vector{Int}.
• face_vertex is left abstract which could easily cause a lot of performance issues. Is it because you don't want something like a Vector{Union{...}}? An enum or a sum type could be good for handling this case efficiently (https://github.com/MasonProtter/SumTypes.jl). I could look at improving this if there is a fixed world of types used. Any particular demo scripts in examples/ you would recommend for benchmarking?