A Proposed Approach for Building Credible DSMs

This section is taken from  (Qi Dong, 1999).

Step 1: Define the system and its scope.

Step 2: List all the system elements.

Step 3: Study the Information Flow between System Elements.

Step 4: Build a matrix to represent the information flow and decide on a suitable measure to be used in the DSM.

Step 5: Give the matrix to the engineers and managers to comment on and use.

Step 1: Define the System and Its Scope.

Since the DSM is a tool that studies the design process as a system with many interacting elements, it is important to define the boundary of the system in order to focus the research work. Different system definition results in different output of the DSM.

Step 2: List All the System Elements.

Initially, the system elements can be chosen based on the existing project plans, engineers’ suggestions, etc. The author usually defines the initial set of system elements based on the reading of design documentation. However, experience shows that the initially defined system elements often need to be modified in the process of assigning interactions to them.

Step 3: Study the Information Flow between System Elements.

The third step is to study the information flow between system elements. The author read the design documents as well as interviewed experienced engineers who were working on the particular product. Interviews are just as important as reading design documents for two reasons. First, not all the knowledge is well captured by design documents. A large amount of information exists in engineers’ heads. Hence, it is important to extract the undocumented knowledge from the engineers. Second, interviews seem to be an effective means of extracting knowledge from the engineers’ mind compared to other methods. During the thesis research work, the author found that different engineers often had different views on how one element related to the other and how important the relation was. The causes of the differences could usually be one of the following two:

• The interaction was not direct. For example, the Belt Seals (in an automotive door assembly) affect the motion of the window Glass by exerting seal drag force on the glass. The seal drag force and the motion of the glass are factors that affect the motor design. Thus the relation is:

  Belt Seals => Glass => Motor.
  

  However, often, the engineers would say the belt seals affected the motor design due to their intuition from work experience. In this situation, the interviewer needs to have a good understanding on the content of the interaction, and explain to the engineers why a mark should be put in row Glass and Column Belt Seals, instead of row Motor and column Belt Seals. Although there is no mark between the Belt Seals and the Motor, the two will reach each other indirectly, which will show in the reachability matrix.

  Sometimes, the indirect interactions might not be found out during the interview. The interviewer needed to document the content of each interaction, and to go through them alone after the interview to sort out indirect relations. By doing so, the interviewer can also gain a good insight to the system, and find out the essence of the information flow.

• The engineers have different perspectives on the issues due to the difference of their work. In this case, the interviewer acted as a mediator. The interviewer should possess the knowledge of the system to some degree, and be able to discuss different viewpoints with different interviewees, or even go back and ask them again, until a common understanding is reached.

For the two reasons mentioned above, it is very important to interview individual engineers face to face for the content of the relations. However, since interviews are usually time-consuming and tedious, many researchers have proposed using survey sheets or collecting information from meetings. These proposed the methods have their advantages and disadvantages.

In some of the previous papers on DSM, the researchers used survey sheets to obtain the engineers’ opinions. The DSM was constructed based on the majority of the votes or the higher level managers’ views. The advantage of using survey sheets is time-efficient. However, many important details may be lost since the survey sheets don’t give explanations on their choices. Also, bias due to work experience cannot be distinguished in a survey sheet.

Meetings open up the opportunities for discussion and understanding which is unavailable from the survey sheets. Meetings also reduced the amount of time for the data collector to get a consensus among engineers. However, it is inevitable that some of the engineers may feel uneasy to speak their mind due to peer pressure, or due to the influence of the rest of the group. Some important data may be lost this way.

Since the DSM is a tool to analyze the design project and to seek improvements, it is important that the data is accurate. The author feels that although talking to engineers in person is time consuming, the interviewer can usually gather accurate information and gain a very good insight to the system. However, when necessary, one may have to trade the speed of data collection with the quality of the data.

Step 2 and Step 3 are highly iterative. Deeper understanding of the system usually results in modification of the initial system elements. The system elements in this thesis research were modified many times during the interviews and documentation readings in order to represent the system accurately.

Step 4: Build a Matrix to Represent the Information Flow.

Initially, a binary DSM can be built to represent the basic dependency structure and information flows between various system elements. A binary DSM serves as a good start for preliminary analysis; however, a better understanding of the system (or project) might require the use of a numerical DSM that will provide better system understanding and allow for more detailed analysis.  

Step 5: Give the matrix to the engineers and managers to comment on and use.

One of the goals of DSM research is to aid the design engineers and engineering managers to understand the design process better and approach the communication more systematically. Hence, the constructed DSM’s are usually given to the engineers and manager to comment on and, maybe, use. The usual response from the engineers and managers was that they were very impressed by the power of the tool. Furthermore, seeing the entire picture of the design process like never before makes them think over their current practice, and seek improvements. 

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