  Gamma-ray bursts (GRBs) are widely believed to be from massive collapsars
and/or compact binary mergers, which accordingly, would generate long and short
GRBs, respectively. The details on this classification scheme have been in
constant debate given more and more observational data available to us. In this
work, we apply a series of data mining methods to studying the potential
classification information contained in the prompt emission of GRBs detected by
the Fermi Gamma-ray Burst Monitor. A tight global correlation is found between
fluence ($f$), peak flux ($F$) and prompt duration ($T_{90}$) which takes the
form of $ \log {\it f}= 0.75 \log T_{90} +0.92 \log F -7.14$. Based on this
correlation, we can define a new parameter $L = 1.66\log T_{90} + 0.84 \log
{\it f} - 0.46 \log F + 3.24$ by linear discriminant analysis that would
distinguish between long and short GRBs with much less ambiguity than $T_{90}$.
We also discussed the three subclasses scheme of GRB classification derived
from clusters analysis based on a Gaussian mixture model, and suggest that,
besides SGRBs, LGRBs may be divided into long-bright gamma-ray bursts (LBGRBs)
and long-faint gamma-ray bursts (LFGRBs), LBGRBs have statistical higher $f$
and $F$ than LFGRBs; further statistical analysis found that LBGRBs also have
higher number of GRB pulses than LFGRBs.
