## 2 Materials and Methods
### Questionnaire Development  
The survey was designed in weekly meetings, and is based on a review of literature, experience, and expertise of the Software Engineering Research Group (GIIS) at the University of Murcia (UMU). We used a 5-point Likert scale, from 1, which means total disagreement, to 5, which means total agreement. The aim was twofold: on the one hand, we investigated the views of the practitioners about the potential effect of certain current issues in software development with respect to sustainability; on the other hand, we also asked the practitioners about the sustainability of the software development process that they apply at work. From the conceptual point of view, therefore, the questionnaire is divided into two parts. We analyzed the state-of-the-art of sustainability in software; the practices were selected according to the findings of other authors (see Table 1). \"Requirements reuse\", \"code reuse\", \"general sustainability policies (how the company operates)\", \"specific sustainability requirements\", \"principles or requirements for usability and user experience in the development of products\", \"principles or requirements for accessibility in the development of products\", \"principles or requirements of internationalization in the development of products\", and \"Consideration of sustainability when software systems and services are purchased or outsourced\" are practices intended to produce an impact on sustainability during the process of software development [14]. \"Agile and lean methodologies\" [15], \"software product lines\" [16], \"testing and continuous integration\" [17], and \"standardization of practices, tools, technical solutions, etc.\" [18] are methodologies and techniques in which analyses and estimations of the power required to produce software are studied. The \"certification in some sustainability standard (for example, International Organization for Standardization-ISO 14001 and/or Eco-Management and Audit Scheme-EMAS)\" was evaluated in Reference [19], revealing that certified organizations carry out energy management practices related to the approach of the paper. \"Cloud computing and virtualization services\" and the \"use of \"green\" data center infrastructures (using renewable energies)\" play an important role for the sustainability of the software development process. In this sense, elements of clouds which contribute to the total energy consumption are discussed in [PERSON] and [PERSON] [20], and a model for minimizing data centers' energy expenses and maximizing the service is proposed, taking into account service-level agreements, the availability of local renewable power generation, and data centers' workloads [21]. \"Big data and data mining\" was incorporated because it is widely recognized as being one of the most powerful drivers to promote productivity, improve efficiency, and support innovation, and because of the analysis that is made concerning green metrics of big data in [PERSON] et al. [22]. Another practice indicated in the survey was the use of the \"Internet of things (IoT)\" during the software development process. IoT serves people in a collaborative manner, enhancing connectivity all over the world. Taking into account the possibility of using the green IoT, a contribution to sustainability can be achieved in software development process [23]. \"Virtual reality and augmented reality\" is another practice that was included in the survey. In [PERSON] and [PERSON] [24], a new software development paradigm focused on people, information, and an environment with augmented reality support is proposed for sustainability in the software. The aforementioned papers illustrate that the practices studied relate to the environmental and technical dimensions of sustainability. We asked practitioners if they applied those practices at work, and if they believed that these alternatives could help companies to be more sustainable. In the second part of the survey, we also included a subset of the statements proposed by [PERSON] et al.