# A Method for Modelling Business-Critical Architecture Decisions in Engineer-to-Order Companies
## 4 Results
### Introducing the Cross-Functional Architecture Matrix
#### 4.1.2 Analysing Cross-Functional Architecture
Since there is no space for both of them in their original position, the washer/dryer orientation is changed to accommodate the new position of the other systems. In Project C, the change in the washer/dryer orientation means that the door to the drum can no longer open properly if it is right-hinged (it would become too cramped between the door and the wall). Therefore, a design change to the washer/dryer is needed to mount the hinge to the door on the other side. Step 2 in Figure 2 concerns the variance between primary engineering and secondary engineering (variance across sheets). This is identified by looking at one sub-system at a time and identifying how changes to the primary technical systems impact the different parts of the value chain in secondary engineering. The following examples in Figure 3 show the identification process of cross-value-chain variance:  
Figure 3: To-be scenario illustrated using the cross-functional architecture matrix (CAM). The designers have to move the toilet/sink combo to make space for the washer/dryer and bathtub. Moving the toilet/sink means that the door has to be moved. When consulting the civil engineer about the bathroom, they report that the most resource-intensive task in their delivery is the engineering and construction of structural elements. Thus, while moving the items inside the bathroom does not impact the structural design, the door location does. Since the door is placed in a structural wall, in Project C, it has to be completely re-engineered with reviews of both statics and the constructability of the new wall element. Moving the toilet and sink to the other side of the room in Project C negatively impacts the plumber. Their work becomes more expensive because the new location is further away from the main water lines. The main water lines cannot be moved because they have to be located close to the kitchen. Thus, the plumber has a longer installation time and higher material costs due to the need for longer pipes. The toilet placement in Project C affects not only the piping of hot/cold water but also the design of the lateral sewer line. Moving the lateral sewer line to the other side of the room means that it has to be connected to the main sewer line with an additional piece running underneath the building. Adding this extra connection means that the contractor in charge of soil work now has additional work to carry out on the foundation, which increases the cost of the project. Finally, even though the washer/dryer unit in Project C is in the same location (it is only turned 90\({}^{\circ}\)), this also has a critical impact on the project. A worker with a special tool is needed to create the hole in the wall for the exhaust outlet of the dryer. In Project C, the drawings for the location of the hole were not updated before they were sent to the worker. This means that the hole was placed in the wrong location. This was discovered only two weeks later when the washer/dryer unit arrived and was test-fitted. However, the worker with the special tool had a long lead time and could not come out to the site to rectify the problem, which led to a one-month delay in the project. This resulted in the customer having to reimburse tenants one month of rent, since the move-in date was postponed. The example presented above shows that the addition of the washer/dryer caused a chain reaction of variation in other technical systems, first, in the placement of the bathtub, which then induced a change in the hinge design of the washer/dryer itself. Furthermore, all the changes to the primary technical systems had a significant impact on multiple business-critical activities in secondary engineering. Thus, both cross-functional and cross-value-chain variances have been identified, and the first criteria had been met. Whether or not the variance in the bath fixture requires a critical architecture decision then depends on the second criterion: does there exist a potential to mitigate the variance by decoupling or clarifying system dependencies?