  With SDO observations and a data-constrained MHD model, we identify a
confined multi-ribbon flare occurred on 2010 October 25 in solar active region
11117 as a magnetic bald patch (BP) flare with strong evidences. From the
photospheric magnetic field observed by SDO/HMI, we find there is indeed
magnetic BPs on the PILs which match parts of the flare ribbons. From the 3D
coronal magnetic field derived from a MHD relaxation model constrained by the
vector magnetograms, we find strikingly good agreement of the BP separatrix
surface (BPSS) footpoints with the flare ribbons, and the BPSS itself with the
hot flaring loop system. Moreover, the triggering of the BP flare can be
attributed to a small flux emergence under the lobe of the BPSS, and the
relevant change of the coronal magnetic field through the flare is well
reproduced by the pre-flare and post-flare MHD solutions, which match the
corresponding pre and post-flare AIA observations, respectively. Our work
contributes to the study of non-typical flares that constitute the majority of
solar flares but cannot be explained by the standard flare model.
