# Privacy Framework for the Development of IoT-Based Systems
## 1 Introduction  
The Internet of Things (IoT) is rapidly becoming one of the most transformative paradigms in the field of information and communication technology. It is increasingly influencing our daily lives in a wide range of areas, including healthcare, smart homes, transport systems, agriculture, industry, and tourism, to name but a few. At its core, the IoT is based on the integration of computing and communication capabilities into everyday objects [1, 2]. These prominent IoT use cases have been made possible by recent technological advances, such as Radio Frequency Identification (RFID) technology and smart sensors, which continuously collect data and send it over the Internet to designated data centers for analysis [3, 4]. By 2025, it is predicted that there will be 55.7 billion connected nodes worldwide, 75% of which will be connected to an IoT system (IoTS) [5]. IoTSs generate a huge amount of data related to many objects, such as plants, environmental elements (e.g., weather), machines, and people. According to the International Data Corporation (IDC), the amount of data generated by these IoT-connected devices will reach 73.1 zettabytes (ZB) by 2025, up from 18.3 ZB in 2019 [6]. This data should be handled carefully as it travels from source nodes and devices to the point where it becomes useful information for end users. A critical issue that needs to be addressed and resolved during this journey is ensuring security and privacy, as the data transmitted may contain sensitiveprivate information, such as health records, location history, banking information, and so on. The use of this vast amount of personal data should therefore be tightly controlled. As a result, legislative and regulatory initiatives, such as the General Data Protection Regulation (GDPR), have been introduced to address such concerns. GDPR establishes a set of rules that must be followed by all parties handling private and personal data of European Union (EU) citizens [7]. It is well known that IoTS development is difficult due to the heterogeneity of these systems, which include hardware devices, span multiple domains, and require multi-device programming [8]. Therefore, enhancing privacy in IoTSs is a complex and challenging task. In addition, creating IoTSs differs from creating conventional information systems (IS) in that the tools, models, and techniques used to build them are inadequate to handle their complexity [9; 10]. For example, while different development methodologies, such as waterfall, spiral, or agile, are successfully used to develop conventional ISs, when applied to the development of IoTSs, some of the limitations arise when addressing the unique aspects of such systems, such as heterogeneity [8; 11]. Several methodologies have been developed specifically for IoTSs, such as Ignite, which is an open-source methodology divided into two phases: (i) strategy execution and (ii) solution delivery. The strategy execution phase focuses on defining and deciding what to build by identifying opportunities, managing them, and initiating projects. The solution delivery phase focuses on delivering the solution to users through a lifecycle of planning, building, and running. Ignite aims to provide IoTSs with best practices in the form of a reusable and technology-agnostic methodology, providing project templates, checklists, and solution architecture schemes to support the design, configuration, and management of IoT projects. It is important to note that Ignite does not provide technical details on software development and testing [12]. Another notable methodology is High-Level Application Development for the IoT, introduced by [PERSON] and [PERSON] [13]. Rooted in academia, the goal of this methodology is to facilitate the development of IoTSs by leveraging model-driven design methodology and sensor network macro programming. Recently, [PERSON] et al. [14] proposed a Test-Driven Development Methodology for IoTSs (TDDM4 IoTS), which focuses on such systems.