## 2 Research Focus and Relevance  
The conceptual design of new complex products is a very challenging task [13]. Various modes that combine creative thinking with logical thinking during the whole process of product conceptualization are envisaged [14]. To handle the complexity of the product conceptualization process, early formulation of the space of intervention (design scope) is necessary [15]. Design boundaries, constraints, and priorities are defined in this respect [16, 17]. Literature reveals a wide range of means and approaches proposed in this respect. It is usual nowadays to consider structured planning tools in the early stages of a design project for defining and quantifying the design problem [18]. Integrated systems of planning methods and methodologies help design engineers create relevant design information before conceptualizing new products [19, 20, 21]. Such frameworks provide data on expressed and latent market requirements [22], support ranking of design requirements and specifications [23, 24, 25], establish design targets [26, 27], determine design priorities in a constrained space of intervention [28], as well as define both technological and economic constraints [27, 29]. This information is input for the conceptual design phase [30, 31]. An extensive pallet of approaches is reported in the literature to support the product conceptualization process (e.g., [32, 33, 34, 35, 19, 30, 36]). The individual and collective experience,creativity, and several other context-related factors contribute to the formulation and selection of the design framework for a given design problem [37; 38; 39; 40]. Methods, methodologies, and technologies increase the chance of getting out reliable results [30; 37; 41]. Positive potentials in defining reliable solutions using conceptual design chains based on existent methods and design principles are analyzed and demonstrated by several works (e.g., [14; 36; 42; 43]). Chaining of the design method is based on different approaches, which vary from physical laws to evolutionary algorithms (e.g., genetic algorithms [44], particle swarm intelligence [45], as well as other stochastic search techniques [35]). In principle, for various design problems, we need to select adequate design methods [46]. In this respect, [37] reveals the importance of having a knowledge-based chain for supporting conceptual design when engineers face multidisciplinary problems. They develop a platform for synthesizing and reusing known design principles and solutions to support this process. For ideas association during the dynamic process of product conceptualization, contributors in [38] propose a cognitive theory of role-playing for modeling the distributed interactions between actors involved in the ideation process and a linking model (DIM-2) of ideas shared in the group. This approach improves idea generation and selection by dynamically combining individual and collective contributions. In the same register of solution formulation, [39] highlights the importance of collaboration in conceptual design using various distributed platforms and means. Other studies, such as those reported by [30; 47], demonstrate the importance of stimulating and managing human creativity in a structured framework during the conceptual design process for defining highly mature and original solutions. It is important to highlight here that optimization in the conceptual phase should not be confused with dimensional optimization or multiobjective optimization, which is the field of traditional optimization theory and operates with quantitative parameters for an already given formulated concept or design [48]. Returning to our research subject, one can conclude that one specificity of the approaches mentioned in the above paragraphs is they mainly focus on qualitative improvements and less on concept optimization.