Event Notification Services (ENS) have an important role in the current context of Smart Cities. The publish-subscribe paradigm is a suitable approach to connect users and service providers. For many private and public services, including transport and emergency services, only some subscribers should receive event notifications. This paper proposes and investigates the performance of a new ENS framework which allows the sending of events to a subset of subscribers with the best conditions to handle it. The event model implemented by the ENS framework is derived from the publish-subscribe approach. It allows the best subscribers to receive the event based on a specific fitness function. An application of the ENS to the transport service is presented. The results show that when the best subscribers are chosen according to a specific desired metric, the travel time can be reduced or the best drivers can be selected. Therefore, this strategy can improve passengers’ experience and optimize service performance.
- Smart Cities ,
- Event notification service,
- Transport service
- Smart cities,
- Network topology,
An Event Notification Service (ENS) became an important component for Smart Cities applications. A simple event notification service provides a mechanism for selecting and delivering events. More specifically, the ENS applies a filtering mechanism against the content of event notifications. Therefore, it will only deliver notifications that contain certain values specified for the event data when the client specifies it through subscription. The selection processes used to determine which of the published notifications are of interest to the subscribers. In addition to serving the interests of customers(i.e. publishers and subscribers), the selection process can also be used by the ENS to optimize network communication. The information that drives the selection process is originated by customers. The delivery processes are responsible for delivering notifications only to the subscribers who have expressed their interest prior to publication.
The main characteristics required for an ENS to be em-ployed in Smart Cities are presented in . Some of these requirements are decentralized architecture, low packet delivery delay, mobility support, and content-based subscription. Clearly, the ENS must be implemented using a distributed system in which the selection and delivering activities are handled by multiples network servers. This architecture can support fault tolerance, load balance, and also overcome problems caused by natural disasters in a Smart City. However, the system complexity increases in a general way.
When the ENS is offered by a set of servers in a distributed architecture, the network topology is an important aspect and it has a strong relationship to event routing. Events should be selected according to the subscriptions and then sent to the subscribers by means of a routing algorithm. If a fixed infrastructure is considered, after the server topology is defined, servers must establish appropriate routing paths to ensure that published events are correctly delivered to all interested parties who have subscriptions to receive them. In a hybrid topology, which uses a fixed communication infrastructure along with mobile infrastructure, mobile subscribers can be notified todo something or they can behave like distributed sensors that collect data and report them to their base station. For example, distributed sensor nodes can report information like average traffic speed, a latent danger, the temperature in a region, the pollution level, among others.
In an ad-hoc network, the routing topology is not always defined a priori, but somehow the events must follow from publishers to subscribers. Typically, in a hybrid architecture, the topology is constantly changing because of node mobility. Depending on the client’s event service subscription, the method of receiving messages, and the network topology of participants, events can be sent in different ways. However, regardless of the topology, the event routing strategy becomes the main component of the ENS.
In this way, this paper presents a framework for ENS that allows the sending of events to a subset of subscribers with the best conditions to handle the event. For many private and public services, including transport and emergency services, only some subscribers should receive event notifications. The event model implemented by the ENS is derived from the the publish-subscribe model and it allows that the most appropriate subscribers receive the event based on a fitness function. The event model represents the set of rules describing communication between ENS publishers and subscribers. The main contribution of this paper is a new generic and efficient event model for publish-subscribe middleware applied for Smart Cities services. An application of the ENS to the transport service is presented
n this paper was presented a selective event model and its implementation through the ENS. The ENS strategy was derived from the publish-subscribe model and it ensures that the best subscriber receives the event based on a fitness function. An application of the ENS for the transport service was presented. It has been shown that choosing the best mobile unit is better than a random choice. In most cases, the BMUstrategy presented a better performance than RMU.
The ENS can be used in other applications for Smart Cities. In a structural health monitoring service, the middleware would be used to notify authorities about the need for intervention. For air quality monitoring, the ENS could be used to alert, in accordance with pre-established levels of pollution, to the competent authorities. The ENS can be expanded to integrate other independent systems by communicating and coexisting within a Smart City. The routing protocol was only one module implemented, other modules can be added, such as data aggregation, and knowledge discovery modules.
The Kavian Scientific Research Association (KSRA) is a non-profit research organization to provide research / educational services in December 2013. The members of the community had formed a virtual group on the Viber social network. The core of the Kavian Scientific Association was formed with these members as founders. These individuals, led by Professor Siavosh Kaviani, decided to launch a scientific / research association with an emphasis on education.
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FULL Paper PDF file:A New Event Model for Event Notification ServicesApplied to Transport Services in Smart Cities
A New Event Model for Event Notification ServicesApplied to Transport Services in Smart Cities
2020 International Conference on Information Networking (ICOIN), Barcelona, Spain, 2020, pp. 202-207,
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Professor Siavosh Kaviani was born in 1961 in Tehran. He had a professorship. He holds a Ph.D. in Software Engineering from the QL University of Software Development Methodology and an honorary Ph.D. from the University of Chelsea.