# Privacy Framework for the Development of IoT-Based Systems
## 5 Proposed Methodological Approach: Planning, Requirements, and Design (PRD)
### Foundations of PRD  
The PRD approach is founded on a combination of best practices that ensure privacy is prioritized throughout the IoTS development lifecycle. It integrates privacy guidelines, a concise set of principles that are continuously reviewed and validated by developers to ensure data protection. The approach also leverages agile methodologies, emphasizing iterative development with user stories to capture evolving requirements and feedback, and promoting flexibility and responsiveness. At its core, our approach aligns with TpM-Pro, which structures the process into clear phases--_business understanding_, _requirements gathering_, and _detailed design_--creating a cohesive framework that balances privacy, user needs, and technical implementation. This integration ensures a privacy-preserving system design while maintaining adaptability and scalability throughout the project. The TpM-Pro approach, proposed and validated by [PERSON] et al. [PERSON] et al. (2017), is a methodical and structured framework that effectively addresses each phase of the development of an IoTS solution. Our main contribution lies in extending the systematic stages of this approach to more effectively extract IoTS privacy concerns, supported by a set of updated guidelines aimed at achieving privacy-enhanced IoTS solutions. To fully understand our approach and its contribution, it is essential to first explain the TpM-Pro approach in detail. TpM-Pro consists of three core steps:  
1. **Considering the Business:** In this initial phase, the business context is thoroughly analyzed to identify the key issues the IoT solution aims to address. The TpM-Pro methodology prioritizes a deep understanding of the solution's business value, ensuring alignment with customer needs. Key considerations during this phase include  
Figure 1: Phases of the proposed PRD approach. The process begins with Planning, followed by Requirements Elicitation, and then Design. Arrows indicate the logical flow between phases and the procedural feedback loops. business requirements, the entities to be measured or controlled, the involvement of specialized expertise, and applicable business rules. To support this process, the TpM-IoT-Canvas tool is used to systematically extract essential requirements and facilitate collaborative planning. This is achieved through a visual model with eight sections: business, justification, benefits, product, things, solution requirements, client, and team. This comprehensive approach ensures that all critical aspects of the business environment are addressed, establishing a strong foundation for the subsequent development phases. 2. **Gathering the Requirements:** In this phase, the process of gathering requirements focuses on breaking down the system into smaller, manageable components to ensure that both business objectives and technical needs are effectively addressed. The business context and the IoT Open-Source Reference Model (IoT-OSRM) serve as foundational frameworks that guide the identification and organization of system elements. The interrelations among these components are carefully analyzed to ensure coherence and alignment throughout the system architecture. Functional and non-functional requirements are defined using a top-down approach, systematically categorizing them across six levels, beginning with sensor nodes and extending to data presentation. At each level, particular attention is dedicated to addressing security and privacy concerns, ultimately resulting in the creation of a Requirements Report, which consolidates all collected information and provides a solid foundation for stakeholder review and approval before the project progresses to the implementation phase. 3. **Implementation:** In this final phase, developers evaluate and select the most appropriate technologies to fulfill the previously defined requirements, following a bottom-up approach that aligns with the IoT-OSRM reference model.