classifying of power transfer distribution factor (PTDF)

Hi,

can anybody help me to classify the power transfer distribution factor
(PTDF) in terms of his place of the theorie.

to explain what i mean i will give an example of what i mean: the
Lagrangian Variables u can classify like this:
Mathematics-Operations Research-Optimisation-linear
Optimisatio-Duality-Lagrange

.... so how would u classify the PTDF??

Physics-... ??? ...-PTDF

I was trying to figure out and i came to a solution like that:

Physics-electro technics-networks-linear circuits-parallel flows-ptdf

i am also not sure if the ptdf is a direct result of Kirchhoff's
current law or how this fits into the picture.

.... i did not study e-tech, so i dont think that this is a very good
classification. can someone give me feedback and maybe a better
classification for ptdf?

thanx Mirco