*2.1. MCDM*

Multi-criteria decision making is an important branch of the decision-making field. There are some common aspects (alternatives and criteria) in MCDM; the typical MCDM problem can be described as follows:

Let *X* = {*<sup>x</sup>*1, *x*72, ··· , *xn*} be a set of alternatives; let *C* = {*<sup>c</sup>*1, *c*2, ··· , *cm*} be a set of criteria values. The decision matrix *D* is an *n* × *m* matrix, in which element *dij* indicates the performance of the alternative *xi* when it is evaluated according to the decision criterion *cj* (*i* = 1, 2, ··· *n*; *j* = 1, 2, ··· *m*.); the decision element *dij* is provided by the expert. It is also assumed that the expert has determined the weight of the criteria (denoted as *<sup>ω</sup>j*, *j* = 1, 2, ··· *m*). There are three steps in utilizing the decision-making technique to rank the alternatives [32]: (1) Provide the relevant criteria and alternatives; (2) Collective information calculation; (3) Rank the alternative according to the collective information.
