## 4 Materials and Methods  
Empirical research methods have been used in the SPLE to evaluate how feasible or efficient a new technique, method, or tool is. These methods allow identifying weaknesses and strengths of a new proposal in a specific time and a real context. Studies in industrial settings allow researchers to evaluate new proposals and give them realistic feedback, making new proposals in SPLE less distant and alien to the practice [34]. Nowadays, there is great attention on the interaction among researchers and the software industry because this relationship is crucial for the production and communication of knowledge [35]. The interaction among the academic-investigative sector and production sectors should be a permanent activity in which they communicate the findings of the research initiatives and proposals to all those interested [35]. [PERSON] et al. [36; 37] propose a model that facilitates collaboration and sharing knowledge among researchers and extra-scientific actors. This transdisciplinary model relates societal problems with scientific problems; it integrates different visions to produce new knowledge and contributes to both societal and scientific progress. From the viewpoint of academia and research groups, there is a great interest to exchange knowledge and experiences with the industry that allow enriching research ideas. Similarly, companies have an interest in improving their processes and products by using innovative ideas. However, this interaction is complex since it requires one to be able to identify common points that lead to shared goals, and it is also necessary to coordinate their schedules, efforts, and costs when an investigative initiative is going to be carried out. A collaborative approach among researchers and people from the productive sector enables spaces to validate research initiatives as long as enterprises can innovate improving aspects such as the productivity and competitiveness of software. The experience presented in this paper is an empirical model about the collaboration among researchers and industrial actors from past experiences of our research groups of the last ten years but applied from the last four years. This model is depicted in Figure 5.  
The first stage is confidence close up among the parts to know interests, problems, and research opportunities. In this stage, researchers use divergent and convergent collaborative patterns and techniques such as brainstorming, prioritization; actors select the more valuable initiatives. The research groups joined three software enterprises prioritizing some ideas related to software architecture, maintenance, testing, and reuse. The research groups started two software product/process line projects answering the three companies because the common difficulty was the lack of clarity about their reuse scope and strategies. In the second stage, the research groups and companies performed several joint activities. For instance, expert talks (architecture, software product lines, and software process lines), collaborative working meetings (using several collaboration patterns), controlled experiments, and workshops about collaboration and software product lines. In the third stage, the CoMeS-SPL case study took place in the Sunset Software House company. It was planned and executed as a pilot project allowing research groups and the company to work concretely around a mutual beneficial activity. Thus, the research groups evaluated CoMeS-SPL in industrial settings. As the main result, Sunset Software House company understood, from multiple viewpoints, its reuse opportunities scoping its first software product line, re-engineering from their product named CORA platform. Among the main research results are papers published in related conferences and workshops [15; 38; 39; 40; 41]. From the Sunset Software House company viewpoint, the CoMeS-SPL method was adopted, particularly the the scope practices, not just for SPL development but for software development in general.