# 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  
When deciding which systems require business-critical architecture decisions, two criteria must be met. First, either cross-functional [6] or cross-value-chain [13] variance needs to be present in the analysed system. Second, there must be the potential to mitigate the variance either by (a) decoupling the dependency between the two varying elements [55] or (b) clarifying their dependency through an interface description [23]. If these two criteria are met, a critical architecture decision is needed to address the variance in the respective elements. Thus, two main types of variance are sought when analysing architecture: cross-functional and cross-value-chain variance. The analysis of the CAM is exemplified in the following section through a hypothetical case of a bathroom design company. It should be noted that the example of custom bathroom deliveries has been selected for pedagogical reasons only--that is, to illustrate the CAM method without confusing the reader with too many technical details. Subsequently, in the case results, the method is applied to an ETO company delivering production facilities. The example company is concerned with the specification and detailed design of bathrooms for multi-family housing. The company delivers one design for all bathrooms in an apartment complex, but the bathroom design will change from apartment complex to apartment complex. The scope of the bathroom design includes all building fixtures, such as showers, sinks, and white goods, as well as tiles, cabinets, plants, and so on. The company does not do in-house design and construction of the structure/building where the bathrooms are situated. They do not install plumbing or electrical systems. All of this is handled by suppliers or contractors further down the value chain. Design changes that impact activities on the construction site are seen by the bathroom company as the most business-critical elements. The company has several anecdotes of budget overruns due to changes in this phase and emphasises that this is the most time-consuming part of the project. The company wishes to better understand why their bathroom projects always end up so expensive and late, which is why they employ the CAM method. As depicted in Figure 2, three of the latest delivered bathroom projects were chosen for the analysis. The business-critical systems mapped in this example consist of a bath fixture, a toilet and sink combo, and a textile care solution. The company offers two bath fixtures: either a bathtub or a shower cabin. The designers require the toilet and sink to be placed next to each other as pairs. Although the company offers only one type of toilet, the sink comes in a square and a rounded variant. This is not included in the mapping, as the variance does not impact the on-site construction phase. Similarly, the floor tiles come in different colours, and cabinets of different sizes are mounted on the wall, but neither has an impact on the business-critical systems or secondary engineering. Lastly, textile care is included, as the company has recently decided to offer a combined washer/dryer unit, which they have not offered in previous projects. Step 1 in this part of the method (see Figure 2) analyses the three bathroom designs to exemplify how cross-functional variance is identified. Figure 2: Generic populated cross-functional architecture matrix (CAM). The numbers on the figure corresponds to an explanation in the text marked with the same number. In Project A, a bathtub is included in the design, whereas, in Project B, the bath fixture has a smaller footprint because the project demands a shower cabin instead of a bathtub. The smaller footprint prompts the salesperson to offer the washer/dryer unit to the customer, who agrees to include it. The washer/dryer unit is placed in the empty space left by the shower. However, in Project C, a problem arises: the design of Project C requires both the washer/dryer unit and the bathtub.