[...] we will be considering three kinds of MS conditions: "if-then" conditions, "positive" conditions, and "negative" conditions [...]. An if-then condition C is a pair of matrices I(C) AND T(C), the "if" and the "then" part of te condition respectively, where I(C) and T(C) are each incompletely specified matrices which have n rows (one for each distinctive feature) and entry "+", "-", or no entry (blank). Further, I(C) and T(C) have the same number of columns and are disjoint [...]. The if-then condition C has the following interpretation: for all matrices M in U such hat I(C) is a sub-matrix of M, C ACCEPTS M if T(C) is also a sub-matrix of M, and C REJECTS M if T(C) is distinct from M; if I(C) is distinct from M, then C accepts M regardless of what T(C) is. [...] intuitively, the if-then condition C says that if a matrix M in U meets condition I(C), then M must also meet conditon T(C) if it is to be accepted by C. [...] EVERY MS RULE R HAS A DIRECT INTERPRETATION AS AN IF-THEN CONDITION C AND CONVERSELY, with SD(R) corresponding to I(C) and SC(R) corresponding to T(C).
- Stanley (2004), a pag.77