if we have known the density functionρ(r),and then we can calculate the total mass of a spherical body. M=integral of ρ. Now we will say that body has mass M, but I think it is wrong. according to special relativity, mass is equal to energy, so we can also say that body has total energy M,but i think it neglects the gravitational bind energy, which is negative, so the total energy(mass) of that body is smaller than M. and if your solve the Schwa. metric , there is a parameter (here we call Ms), and we define Ms as the mass(or energy) of central body , and I think it includes the energy of binding energy , so Ms is the total energy(mass )of central body, which is not defined by integral ρ, and maybe you can use integral ρ to calculate the mass(energy) of that, but it must larger than Ms. but i have read many papers and books, they all use that integral ρ to represent the mass of body, like a star How is that????、