# Revisiting Problem-Solution Co-Evolution in the Context of Team Conceptual Design Activity
## 4 Discussion
### Revisiting Co-Evolution
A similar pattern can be discerned in the protocols of [PERSON] and [PERSON] [41], who analysed the entire process of teams executing a conceptual design task. This move from problems to solutions is accompanied by a gradual but significant decrease in synthesis and increase in analysis and evaluation of design entities [43]. More precisely, the initially higher proportions of synthesis cycles (divergent process) get gradually substituted by the alternation of analysis and evaluation design operations (convergent process). Commitments made in the conceptual design stage are mainly functional, and designers typically specify the realisation of the solution as they approach the latter stages of conceptual design [98]. By developing the information on how the design works, not only is the problem reduced, but it is also easier for teams to determine \"what can go wrong\" [98] and conduct solution evaluation. Studies also show that new requirements during conceptual design result mainly from the analysis of proposed solutions and that the process of requirement identification is closely related to solution synthesis [92]. As design problem formulations get more precise, the increase of solution evaluation is crucial for successful concept development [99]. Interestingly, the alternation of analysis and synthesis is fairly persistent throughout all of the activity protocols. Besides, the sequence analysis has shown that analysis is most probable to be followed by synthesis and vice versa. These probabilities again point out the critical role of analysis-synthesis cycle for concept generation, as proposed by some studies [51; 63; 74; 100; 101]. It must, however, be noted that some studies also include evaluation as part of the analysis. Nevertheless, it can be argued that fractions of the design process where sequences of analysis and synthesis design operations alternate [43] appear consistently throughout team conceptual design activities. This is  
Figure 8: Cumulative number of problem and solution entities generated by all teams throughout the ideation and concept review experimental sessions. because in design teamwork, the analysis is essential for the better understanding of team members, and leads to progress in design activity, whether it is used as clarification [42; 102] or questioning [74]. Hence, achieving common ground (understanding) appears to be a vital ingredient of a team's creative process during conceptual design activities [103]. As such, the analysis plays an important role both during the divergent activity fragments, where design problems and solution evolve together at a high pace, but also during the convergent fragments, where solutions are evaluated and refined. During the former, problem space exploration often results in new solutions, whereas solution space exploration results in new problems. During the latter, however, the co-evolution episodes occur less often, and new solution entities are mainly a result of convergent refinement. The above-explained phenomena were summarised in the form of a hypothesised model shown in Figure 9. The model depicts the increase in the number of new problem and solution entities generated during team activities as the conceptual design phase progresses. In the beginning, the rate at which team members generate new entities is high for both design problems and solutions. This is the divergent part of the process, where the pace of design space exploration is fast, and the two spaces co-evolve. Most of the synthesised problem entities follow problem space exploration, and most of the synthesised solution entities follow solution space exploration. However, what characterises this part as dominantly co-evolution (see Figure 8) is that teams switch between the problem and solution space very often, with most of these inter-space transitions being the synthesis of design entities.