This paper explores the concept of sensing as a service (SaaS) in the context of Smart Cities supported by the Internet of Things (IoT). The rapid growth of the global population has placed significant pressure on urban living, prompting the need for efficient city management. Smart Cities aim to address challenges such as waste, traffic, energy, and health through information and communication technologies (ICT). IoT, which connects billions of sensors to the Internet, is a key enabler of Smart Cities. The SaaS model allows for the efficient and effective use of sensor data by enabling the sharing and reuse of sensor data across different stakeholders. The SaaS model is structured into four layers: sensors and sensor owners, sensor publishers, extended service providers, and sensor data consumers. Each layer plays a distinct role in the model, with sensor owners deciding whether to publish their data, sensor publishers facilitating data sharing, extended service providers offering additional services, and sensor data consumers utilizing the data for various applications. The paper discusses a futuristic scenario where a refrigerator in a smart home uses sensors to share data with a sensor publisher, allowing a company to access data for marketing purposes. This scenario illustrates the interactions between different parties in the SaaS model. The paper also presents three use case scenarios: waste management, smart agriculture, and environmental management. In waste management, the SaaS model enables cost-effective data sharing among city authorities, recycling companies, and health and safety organizations. In smart agriculture, the model supports collaborative research and data sharing across different institutions. In environmental management, the model allows for the use of existing sensors to monitor and manage environmental conditions. The SaaS model offers several advantages, including cost reduction, data sharing, and innovation. It also provides real-time data for decision-making and policy-making, and supports privacy preservation by allowing sensor owners to control their data. However, the model faces challenges in technological, economic, and social aspects that need to be addressed for its successful implementation.This paper explores the concept of sensing as a service (SaaS) in the context of Smart Cities supported by the Internet of Things (IoT). The rapid growth of the global population has placed significant pressure on urban living, prompting the need for efficient city management. Smart Cities aim to address challenges such as waste, traffic, energy, and health through information and communication technologies (ICT). IoT, which connects billions of sensors to the Internet, is a key enabler of Smart Cities. The SaaS model allows for the efficient and effective use of sensor data by enabling the sharing and reuse of sensor data across different stakeholders. The SaaS model is structured into four layers: sensors and sensor owners, sensor publishers, extended service providers, and sensor data consumers. Each layer plays a distinct role in the model, with sensor owners deciding whether to publish their data, sensor publishers facilitating data sharing, extended service providers offering additional services, and sensor data consumers utilizing the data for various applications. The paper discusses a futuristic scenario where a refrigerator in a smart home uses sensors to share data with a sensor publisher, allowing a company to access data for marketing purposes. This scenario illustrates the interactions between different parties in the SaaS model. The paper also presents three use case scenarios: waste management, smart agriculture, and environmental management. In waste management, the SaaS model enables cost-effective data sharing among city authorities, recycling companies, and health and safety organizations. In smart agriculture, the model supports collaborative research and data sharing across different institutions. In environmental management, the model allows for the use of existing sensors to monitor and manage environmental conditions. The SaaS model offers several advantages, including cost reduction, data sharing, and innovation. It also provides real-time data for decision-making and policy-making, and supports privacy preservation by allowing sensor owners to control their data. However, the model faces challenges in technological, economic, and social aspects that need to be addressed for its successful implementation.