You can measure public opinion on key issues and services such as public transportation ,education ,emergency response and water management, cleanliness by tapping into social media .
An important role for sentiment mining in smart cities would be to assess the public's attitude to the city administrator's products, services and policies. By mining sentiment from social media, for example, it should be possible to gauge the public's feelings concerning the current provision of services. By refining the analysis to include possible changes in products and services, it may be possible to steer policy in a better direction. Sentiment can also be mined to assess the public's attitude to the city's administration more directly: how are the actions and polices of the administration being perceived by the public, how popular is the administration? By incorporating a taxonomy of polices, products and services, along with appropriate positive and negative sentiment words and phrases, it would be possible to automate a comprehensive sentiment analysis to guide the policy making process and improve the cities provision of products and services.
Sentiment Mining is playing a major role in giving opinions of people all over the world and one can get better idea about it or one can get little bit knowledge about it. Opinions of other shave always affected people. so getting this from over all people about the product or anything one is looking for is better than anything one can know.