## 3 Research Approach  
The research approach was based on a literature review combined with a case study. The findings of both the related work review and the literature review were used to provide guidance in the case study planning. The literature review, see Section 4, had the aim to reveal: challenges, opportunities, supporting pillars, and emerging trends within development of automation systems based on SOA or not. The review had its focus on recent literature, from 2017 to 2021, but also a limited number of older literature of interest were reviewed. The search of the review had a general start and was then narrowed down to key contributions for professional automation systems. The sequences of key words used in the searches were:  
* Automation system development, 3,230,000 hits, 30 reviewed (a lot concerned home automation and not professional automation systems);
* soa automation system development, 52,100 hits, 30 reviewed;
* soa \"automation system\" development, 2940 hits, 40 reviewed;
* soa \"automation solution\" development, 262 hits, 40 reviewed. The aim of the case study was to continue with the findings and look deeper into why organizations and companies consider it is a good idea to develop automation systems using an SOA-based platform. The case-study methodology used was as proposed by [PERSON] (2018) with \"a linear but iterative process\" (p. 1) comprising: planning, design, preparation, data collection, data analysis, and sharing of results. The case study was conducted between 2017-2021 and comprised five cases which are further outlined below. The research question is \"How many improvements have been made using an SOA-based platform, compared to traditional development, and where in the lifecycle are the improvements embodied?\". The \"how\" in the research question indicates that a case-study methodology is appropriate to use. In addition, a case-study methodology was suitable, as the researchers did not directly participate in the work spanning multiple contexts and development cases. The case-study cases involved both companies and a major EU-funded research project, Arrowhead Tools, as outlined below:  
* Arrowhead Tools is a large-scale EU RDI project mainly funded by ECSEL with a total budget of M Euro 91 (Available online: [[https://arrowhead.eu/arrowheadtools/news/europe-s-largest-project-for-digitization-of-industry/](https://arrowhead.eu/arrowheadtools/news/europe-s-largest-project-for-digitization-of-industry/)]([https://arrowhead.eu/arrowheadtools/news/europe-s-largest-project-for-digitization-of-industry/](https://arrowhead.eu/arrowheadtools/news/europe-s-largest-project-for-digitization-of-industry/)) accessed on 9 December 2021). Arrowhead Tools aims to create engineering tools for the next generation of solutionsin digitalization and automation for the European industry. The data collected targets more than 30 use cases conducted, as part of the project work, in various manufacturing and process industry contexts. Data were collected as part of the project work during 2020-2021. The predecessor projects to Arrowhead Tools, e.g., Arrowhead and Productive 4.0, have resulted in an SOA-based automation platform named Arrowhead Framework [19] and the Arrowhead Tools project adds usable tools to increase the usability of the Arrowhead Framework in industrial settings. Since 2006, a string of RDI projects preceded these 3 projects, where initial concepts and ideas were crafted. * LKAB is a mining company located in Sweden and is very active in development of the future smart, digitalized, and sustainable mining at great depths. Further, LKAB is very active in developing production processes for fossil-free steel production based on hydrogen and electricity. Data were collected during 2021. LKAB develops its own automation/middleware platform, named LOMI (LKAB Open Mine Integrator). * Sinetiq AB is a recent spin-off from BnearIT AB and is a high-tech SME located in Sweden and active in the Swedish market.