  We describe a new approach to the canonical decompositions of 3-manifolds
along tori and annuli due to Jaco-Shalen and Johannson (with ideas from
Waldhausen) - the so-called JSJ-decomposition theorem. This approach gives an
accessible proof of the decomposition theorem; in particular it does not use
the annulus-torus theorems, and the theory of Seifert fibrations does not need
to be developed in advance.
