# Function-Oriented Applicability Evaluation of Technical Folding Based on Expert Knowledge
## 7 Discussion and Conclusions  
Despite its promising potential, technical folding has rarely been implemented in technical systems so far. This is often due to a lack of expertise and experience on the part of engineers, who are unable to apply the solution principle to their current task during concept development. Inexperienced product developers tend to choose known solution principles instead of utilising the potential of technical folding. To overcome these challenges, the research paper developed the EvalTech method and implemented it in a software application for efficient utilisation. EvalTech helps inexperienced product developers to decide whether the solution principle of technical folding and which classification of technical folding systems can be used in concept development. This applicability evaluation was performed on the basis of functions and function structures of successfully developed folding systems from the literature. The research focused on answering the research question of how function structures can be used as databases for applicability evaluation.  
To answer the research question, first functions of existing technical folding systems were derived from literature. Then, functions were formalised using the subject-verb method and stored in a database (_case base 1_). The machine-readable subject and verb of a function were used as attributes for the similarity calculations between functions of the new technical problem and characteristic functions of technical folding. Hierarchical function structures were formalised using functions of _case base 1_ and directed graphs between functions and stored in another database (_case base 2_). The graph-based relationship between functions in the hierarchical levels was used as an attribute for the similarity calculation between function structures of the new technical problem and function structures of technical folding.  
The equations for the similarity calculations were each defined using the machine-learning method _nearest neighbour_. The result of the similarity calculation between functions depends strongly on the selected words. Functions that are described with synonymous words or contain grammatical errors or errors in their spelling cannot be considered in the similarity calculation. In contrast, the similarity calculation between function structures is more precise. The results of both similarity calculations are values between 0 (=not similar) and 1 (=identical). So far, however, the software application does not provide a purely objective recommendation as to which similarity value makes an application successful. Instead, in addition to the similarity value, the software application presents the assigned technical folding system with its properties, such as the overall purpose or the direction of movement. The final decision is therefore not made by the computer alone, but also by humans.  
The developed similarity calculations and _case bases_ are used as part of the CBR process, _retrieving_, and its specific subprocesses according to [PERSON] and [PERSON] [29]. The subprocesses of _retrieving_ are implemented in a software application for the efficient support of inexperienced developers. The implementation of the further _reusing_ and _reusing_ based on the result of the applicability evaluation is not covered by the software application. Nevertheless, based on the visualised concepts of known folding systems, it is possible to design your own development task by analogy.  
The EvalTech method developed was initially tested using the concept development of a covering for industrial robots. The result of the initial evaluation of technological fit was also tested using the successfully realised concepts of known technical folding systems. The EvalTech method and its implementation in software is limited to the evaluation of only one solution principle, namely the technical folding.