# Enhancing Sustainable IoT Systems Through a Goal-Oriented Requirements Analysis Framework
## 4 Goal-Oriented Requirements Analysis Approach for IoT Software Systems
### Application Example: IoT System for Monitoring Air Quality
#### 4.2.5 QVT for Model-to-Model Transformations
Despite these contributions, a recurring limitation in all surveyed methods is the absence of a systematic and explicit integration of sustainability as a first-class modeling concern. Specifically, most frameworks lack the ability to quantitatively represent and trace sustainability-related requirements, such as energy efficiency, device longevity, and environmental impact, throughout the software development lifecycle. The GORA methodology explicitly addresses this deficiency by embedding sustainability dimensions--environmental, economic, and social--within the goal-modeling process, leveraging the \(i^{*}\) framework. It extends this foundation by introducing quantifiable Key Performance Indicators (KPIs) and enabling their transformation through model-to-model (QVT) and model-to-text (Acceleo) pipelines. This approach ensures that sustainability objectives, such as reducing energy consumption or promoting device reuse, are not only explicitly modeled, but are also systematically propagated and preserved from early-stage requirements analysis to the generation of executable Python code. In contrast to existing methodologies, GORA provides robust support for the traceability and operationalization of sustainability-related goals by tightly integrating them into the RE and MDD layers. Consequently, it not only fulfills traditional functional and non-functional requirements, but also guarantees that sustainability is systematically modeled, monitored, and enforced. This positions GORA as a novel and pioneering framework within the emerging domain of sustainable IoT software engineering. A summary of this comparative evaluation between the representative methodologies identified in the literature is presented in Table 2.

The results demonstrate that the GORA methodology is uniquely suited to support the development of sustainable smart home systems by seamlessly integrating goal modeling, model transformations, and automated code generation within a fully traceable end-to-end development process. In contrast to approaches such as SysML+RELAX, which prioritize adaptive behavior, or FORM-L, which focuses on formal verification, GORA explicitly connects sustainability objectives with executable system logic (all while preserving accessibility for non-expert developers and rapid prototyping contexts). However, it is important to acknowledge that the current scope of GORA does not encompass features such as dynamic real-time reconfiguration or formal verification, capabilities that are integral to frameworks like RELAX and FORM-L. Future research may explore the integration of such mechanisms to broaden the applicability of GORA in highly dynamic and adaptive IoT environments, thus reinforcing its potential as a comprehensive solution for sustainable system engineering. ## 7 Conclusions and Future Work

Defining a comprehensive SE methodology that encompasses the various phases of RE within the IoT domain is a highly complex task. This undertaking requires a robust foundation built on empirical evidence to effectively address the challenges associated with developing IoT solutions, including device connectivity, data management, end user interaction, and system monitoring. Ensuring that IoT projects are meticulously planned, executed, and maintained is fundamental to achieving their intended objectives. Furthermore, such a methodology should be complemented by a well-defined set of models and tools aligned with the core principles of the paradigm, ultimately facilitating the development of sustainable and adaptable IoT systems. As discussed in Section 2, previous proposals have considered various RE phases; however, they were often tailored to specific domains of IoT application, such as healthcare, disaster management, control systems, or building automation. A significant gap remains in the availability of generic methodologies for IoT software development that comprehensively cover the standard RE phases, including elicitation, analysis, specification, validation, and management.