  Signature-based algorithms is a popular kind of algorithms for computing
Gr\"obner bases, and many related papers have been published recently. In this
paper, no new signature-based algorithms and no new proofs are presented.
Instead, a view of signature-based algorithms is given, that is,
signature-based algorithms can be regarded as an extended version of the famous
MMM algorithm. By this view, this paper aims to give an easier way to
understand signature-based Gr\"obner basis algorithms.
