A Study on Publish-Subscribe Middlewares for Selective Notification Delivery in Smart Cities

A publish-subscribe middleware is an application-independent infrastructure that supports implementing event-based systems, in which event generators (i. e., publishers) notify events to the infrastructure and event consumers (i. e., subscribers) subscribe to the infrastructure for receiving relevant notifications. Subscribers are not directly addressable by the publisher but are indirectly addressed according to the content of the events. This anonymity ensures that publishers and subscribers exchange information without knowing each other, which allows middleware to expand to a massive size on the scale of the Internet and Smart Cities. In this way, this article presents a study on publish-subscribe middlewares for the selective sending of events in Smart Cities. This selective notification delivery is important for some applications such as emergency services in Smart Cities, where only a subset of subscribers should receive the event and handle it as soon as possible.