## 5 New Taxonomy for Constructability Constraints and Features
### Validation of the Refined Computational Design Approach by Cross-Referencing Existing Research  
The primary objective of the presented conceptual computational design approach in this section is to address the lack of a structured method for integrating constructability knowledge at the micro, meso, and macro levels into the computational design process.  
The proposed activities in this approach are designed to minimally disrupt common computational practices, introducing minor yet effective enhancements to the existing methods familiar to practitioners, which are anticipated to make its adoption more appealing by aligning with current workflows.  
While the idea of more frequent and early engagement of domain experts in the design process is not novel, the new taxonomy introduced in this research sets this approach apart from the common computational design methods currently used in the industry. Therefore, validating the refined computational design approach involves two main pillars: first, the validation of the new taxonomy, as presented in the previous section, and second, the validation of the proposed activities for integrating experts' knowledge, which is discussed in the remainder of this section.  
The cross-referencing methodology is employed to validate the proposed new activities outlined above. Existing research highlights that engaging downstream experts during the design process, such as builders, manufacturers, and field trades, is particularly feasible for projects involving prefabricated elements [3; 41; 81]. However, this engagement requires the implementation of appropriate collaborative project delivery methods [41; 82] and the establishment of collaborative infrastructure, particularly through BIM platforms [41; 83; 84]. The importance of collaborative construction practices was further emphasized in all four external projects introduced in the previous section. Thus, it can be concluded that the early involvement of downstream experts during the design process is a valid assumption.  
Conversely, the lack of such necessary collaborative construction practices for effective practitioner engagement can create notable inefficiencies. This was partially the case in the OC project, which led to multiple constructability challenges on site, as observed by the research team and raised by the practitioners during the interviews conducted. The main two reasons frequently mentioned in these interviews were:  
1. A traditional delivery model that did not allow practitioners to freely and frequently exchange with one another.
2. A lack of maturity in the project team, with the exception of the design team, in terms of using BIM.  
Examples of the missing constructability features mentioned by the practitioners in the OC project are:* The placement of the connections on the panels could have been optimized further with the sufficient engagement of the manufacturer. In fact, the manufacturer modified the suggested placements to facilitate the fabrication process, leading to issues during the installation.
* The arrangement of the connections on each panel had a high variance, resulting in confusion on site when choosing the right panel, as panels of the same type could have different arrangements of connections.
* The order of the placement of the panels on the trucks could have been organized to follow the installation sequence, avoiding unnecessary crane and crew time on site.