A time-based DSM is akin to a precedence diagram or the matrix representation of a directed graph. In time-based DSMs, the ordering of the rows and columns indicates a flow through time: earlier activities in a process appear in the upper-left of the DSM and later activities appear in the lower-right. Terms like “feedforward” and “feedback” become meaningful when referring to interfaces. A feedback mark is an above-diagonal mark (when rows represent output). Time-based DSMs are typically analyzed using sequencing algorithms, that reorder the matrix elements to minimize the amount of feedback marks, and make them as close as possible to the diagonal.