# Systematic Literature Review of System Models for Technical System Development
## 4 Discussion
### Drivers and Indicators for the Usage of System Models
Overall, our analysis shows that system models are viewed as a sufficient tool to synthesize and analyze technical systems across various industries and domains, despite being seen as novel and to a degree often still experimental. A precise definition of the term system model remains elusive, yet there are certain key aspects in regards to the purpose system modeling should serve, that we were able to extract. Overall system modeling is applied to manage complexity in system development and unify as well as align different domains of system development. Depending on the author's perspective and the context, this can manifest itself as improved consistency, improved communication, improve collaboration or other terms that all describe a concerted effort by an organization to develop a technical system. For practitioners in engineering, the issue of system modeling and specifically how to utilize a system model is largely need-driven, without much emphasis on the definitions and boundaries that are of potential interest to academia and systems theory research. This becomes even more clear when considering the relative variety of implied definitions of the term system model. This need-driven and basically problem-solving-oriented view in the industry appears to also be reinforced by a largely bottom-up approach to systems modeling. Across all industries, explicit generic system modeling efforts through graphic modeling languages such as SysML, OPM and others are gaining traction, which are often associated with MBSE. Regarding incorporating behavioral and dynamic system characteristics, though, the architectures encountered in the body of literature draw significantly from established methods and models used in different engineering domains. For both modeling solution vendors as well as engineers ultimately only the outcome matters. Due to the need-based and often bottom-up approach to system modeling in engineering, there is a considerable risk of missing publications that simply make use of different verbiage to describe their understanding of system models and their applications. Furthermore, non-peer-reviewed engineering magazines could contain more information regarding the use and understanding of system models in different industries, but those sources were mostly not searchable or otherwise indexed and were not included in the initial key word search. This review sought to lower this risk by using a relatively wide range of keywords and putting more emphasis on manual review of a larger literature body. Across the body of the literature review, a wide range of either, very explicit or implicit statements were made regarding system models, their purpose, definition, general usage as well as unique use cases described. Quite often defining and describing the system model is not the main focus of publications and systems modeling is merely established and described as a solution to a problem, which is then described in further detail. In addition to information about the scope of the review being embedded within other subjects of research in engineering and technology, some publications mentioned keywords of our search exclusively in their abstract without mentioning them in the actual text, or if so, only implicitly and hard to extract through automated methods, which was another driver for our focus on manual review of a less exclusive body of literature as opposed to a very restrictive keyword search.