{'fraction_non_alphanumeric': 0.022465088038858532, 'fraction_numerical': 0.013054037644201578, 'mean_word_length': 5.537698412698413, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Conceptualisation and formalisation of technical functions

In the engineering design research community, function-based descriptions have become a popular means to describe products and systems using abstract building blocks. A claimed advantage is that they allow designers to synthesise and describe their designs early in the design process without having to consider physical principles, material selection, and geometric shapes and features. In addition, they can be used for critical investigation of both unfinished designs and existing products, in which case functions are supposed to facilitate decoupling of perceived needs of end users from concrete solution elements. This solution independence has been said to encourage out-of-the-box thinking and thus increase creativity and innovation, both in novel designs and in redesign. In order to facilitate a comprehensive investigation of the functional capabilities of products, the technical functions are often taken into consideration together with the utility functions. In the case of the development of new products or components, technical functions are the building blocks or elements of a solution independent functional synthesis, which is typically followed by the investigation of possible realisations of functions and converting the functional schemes into feasible component structures and numerically testable virtual and physical prototypes. Since the mid-twentieth century a large number of publications have appeared on technical functions. Figure 1 illustrates that the number of scientific articles referring to technical functions has dramatically increased since the early 1990s. Academic debate on functions in design and engineering has also been the topic for several special issues of various journals. These have been edited by Sticklen and Bond (1991), Kumar (1994), Chakrabarti and Blessing (1996), Chittaro and Kumar (1998), Stone and Chakrabarti (2005) and Kroes and Meijers (2006). Despite the growing attention that technical functions receive in academia, they are not widely used by designers and have hardly been incorporated in computer tools developed for industrial users. As Birkhofer (2011) stated, ‘there is an urgent need to close the gap between conceptual approaches in design methodology and the involvement in embodiment and detailed design in design practice’. In a recent survey of design synthesis systems by Chakrabarti et al. (2011), the state-of-the-art computer tools for function-based synthesis were reviewed and it was concluded that, among other things, (i) the systems need to be scaled-up to support problem solving at the levels of complexity expected in practice and (ii) a better understanding is needed on how the systems can be integrated into current design processes in practice. In addition, it was found that rigorous means for evaluating the systems are missing, and that still no commonly accepted terminology is available to foster exchange of research models, methods and results. The extensive criticism that the whole concept of ‘technical function’ has been receiving in recent years underpins and explains the critique and reservations towards computer-based functional design systems. Horváth (2000) identified 12 areas where scientific understanding is