  We discuss methods used to interpret the measurements of CP-asymmetry in
B->pi+pi- within the framework of the Standard Model. Interpretations using
various theoretical inputs are given, ranging from the rather general, yet
unpredictive, properties based on strong isospin symmetry to highly predictive
calculations using QCD Factorization. The calculations are performed using the
software package CKMFitter and a frequentist method, Rfit.
