  In this paper, an integrated theory of the probe and singular sources methods
for an inverse obstacle problem governed by the Stokes system in a bounded
domain is developed. The main results consist of: the probe method for the
Stokes system; the singular sources method by using the notion of the probe
method; the completely integrated version of the probe and singular sources
methods. In establishing the singular sources method, a third indicator
function which is called the IPS function plays the central role.
