Suitability of product development methods for hybrid products as bundles of classic products, software and service elements

The requirements engineering of hybrid products is an important field that still has a paucity of investigation to date. This paper analyzes the suitability of product development methods for the requirements engineering (RE) of hybrid products. The strengths and shortcomings of these methods regarding hybrid products are stated and fields of improvement are derived. To successfully differentiate from competitors, classic products are no longer sufficient. Therefore, many companies offer holistic solutions to customers' problems. These solutions consist of bundles of classic products, software and services called hybrid products or product service systems (PSS). Hybrid products are characterized by a high number of components that are developed by different disciplines, by a high degree of technological integration and by a high degree of customer-integration. Due to their unique characteristics, hybrid products need holistic handling. Especially interesting is the specification and handling of the requirements for hybrid products called requirements engineering. This phase of the development process is very important for the later success of the product. The characteristics of hybrid products were thoroughly analyzed, and requirements of the RE for hybrid products were derived. A structured literature review was carried out to find the state-of-the-art of RE in product development including common textbooks and publications on respected conferences and journals in product engineering. In total, 15 textbooks, 79 journal articles and 137 articles of conference proceedings were analyzed. This provided the state-of-the-art of RE indicating the approaches used. An important aspect of the research was the matching of these approaches to the requirements defined earlier. This resulted in a list of 13 fields of RE presenting the strengths and shortcomings of the approaches in detail from which two major fields of improvement could be derived, those which need to be addressed in practice. The results show that RE for hybrid products has special needs, particularly in interdisciplinary cooperation and customer integration. The methods for RE in product development are well elaborated upon, but need to be adapted to hybrid products. There is a need for further analysis and integration of RE into the overall development process of hybrid products, as well as further development of hybrid products in practice.