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The design structure matrix (DSM) is a system modeling tool. It has two main strengths. First, it can represent a large number of system elements and their relationships in a compact way that highlights important patterns in the data (such as feedback loops and modules). Second, it is amenable to matrix-based analysis techniques, which can be used to improve the structure of the system.
A DSM is a square matrix (see figure). The cells along the diagonal represent the system elements, which are often labeled in the rows to the left of the matrix and/or in the columns above the matrix. The off-diagonal cells are used to indicate relationships between the elements.
Two conventions for entering the off-diagonal marks have been used. In one, reading across a row reveals what other elements the element in that row provides outputs to, and scanning a column reveals what other elements the element in that column receives inputs from. Thus, in the figure, element B provides something to elements A, C, D, F, H, and I, and it depends on something from elements C, D, F, and H. In the other (opposite) convention, which is just the transpose of the matrix, inputs are shown in the rows and outputs in the columns. The two conventions convey equivalent information.
Two main categories of DSMs have been proposed: static and time-based. Static DSMs represent systems where all of the elements exist simultaneously, such as components of a product architecture or groups in an organization. Static DSMs are usually analyzed with clustering algorithms. In time-based DSMs, the ordering of the rows and columns indicates a flow through time: upstream activities in a process (in the upper-left of the DSM) precede downstream activities (in the lower-right), and terms like “feedforward” and “feedback” become meaningful when referring to interfaces. Time-based DSMs are typically analyzed using sequencing algorithms.
DSMs stem from diverse roots. A static DSM is often equivalent to an N-square diagram or an incidence matrix. The time-based DSM (and the "DSM" term itself) originated with Don Steward, who coined the term “design structure matrix” in the 1960s. Steward's DSM grew from the use of matrices to solve mathematical systems of equations. A time-based DSM is akin to a precedence diagram or the matrix representation of a directed graph. The terms dependency structure matrix, dependency source matrix, dependency map, interaction matrix, and others are also used in the literature. The point of the matrix is to illuminate the structure and aid in the analysis of modeled systems such as products, processes, and organizations.
The use of DSMs in both research and industrial practice increased greatly in the 1990s. DSMs have been applied in the building construction, semiconductor, automotive, photographic, aerospace, telecom, small-scale manufacturing, factory equipment, and electronics industries, to name a few, as well as in many government agencies.
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