[Show abstract][Hide abstract] ABSTRACT: Many applications in the Internet of Things (IoT) depend on the occurrences of events with temporal and spatial constraints to determine the further actions. A major challenge encountered is how to specify and detect the spatio-temporal events. The paper adopts Pub/Sub middleware to help IoT applications to capture spatio-temporal events. Specifically, the paper presents a composite subscription language CPSL and builds the corresponding Pub/Sub middleware Grus. The subscriptions in CPSL can specify diverse temporal, spatial and logical relationships of events, in particular, can describe the moving events related to mobile objects, and Grus is responsible for detecting whether events are matched with subscriptions in a distributed way. In addition, Grus provides the optimization strategies for subscriptions involving unary spatial operators. The paper also evaluates Grus's matching performance and costs through simulation experiments. The experimental results show that Grus can achieve satisfying performance and acceptable overheads, and the optimization strategies can efficiently speed up the detection of spatial events.
No preview · Article · Apr 2013 · Decision Support Systems
[Show abstract][Hide abstract] ABSTRACT: In pervasive environments, the Pub/Sub paradigm is regarded as an important means of information sharing and event dissemination.
In this paper, we first analyze different context in Pub/Sub systems that has remarkable impacts upon user’s satisfaction
to event dissemination and then give corresponding strategies by exploiting time context and event-preference context so as
to provide personalized event dissemination. That is, by leveraging time context, we provide the extended matching against
long-standing events, and by leveraging event-preference context, we present the recommendation algorithm which is based on
hidden Markov process. Performance analysis and experiment evaluation show that both strategies can improve user’s experiences
of event dissemination.
No preview · Article · Mar 2011 · Personal and Ubiquitous Computing
[Show abstract][Hide abstract] ABSTRACT: For constructing a Pub/Sub middleware to detect and disseminate events in the Internet of Things (IoT), we have to pay close attention to the following requirements: (1) the IoT applications usually care about the events with both spatial and temporal extents, (2) It must address the issues brought by the IoT features, such as autonomy embedded in collaboration among things, dynamics implied by running environments. In this paper, we provide a concise and expressive formulation for the events in IoT, i.e. complex spatio-temporal events. We also present the architecture of the corresponding Pub/Sub middleware, which aims at achieving the desired functionality and efficiency.
[Show abstract][Hide abstract] ABSTRACT: Pub/Sub systems permit users to submit subscriptions and notify interested users of the events detected in a distributed way. Moving a Pub/Sub system to a cloud infrastructure is for high performance and scalability. This paper describes how to migrate two Pub/Sub systems i.e. PADRES and Once Pub Sub to Xen Cloud Platform, especially proposes black-box method, grey-box method and white-box method so as to take full advantage of cloud mechanisms. This paper then conducts a series of experiments on the Pub/Sub systems in the cloud to evaluate benefits and costs. The experimental results indicate that the black-box method does not always take effect although it can be implemented easily, the grey-box method is more appropriate to a Pub/Sub system if its workload features and brokers' roles are known in advance. Further, the experimental results show the white-box method, combined the load balance mechanism both in the cloud and in a Pub/Sub system, can achieve satisfying performance and scalability especially facing the workload with unidentified distribution.
[Show abstract][Hide abstract] ABSTRACT: In Pub/Sub systems, channel-based approaches to routing the subscriptions and events have many advantages such as fewer routing messages, lower costs for subscription management, etc. But a potential issue embedded in this kind of approach, i.e. loadings on different event brokers are apt to unbalancing, is ignored more or less. In this paper, we design a load balancing mechanism and integrate it into a channel-based approach in a Pub/Sub system. In particular, we define a balancing state in a Pub/Sub system, and then propose the balancing control initiation algorithm which decides not only whether to perform load balancing among event brokers but also whether to adjust the number of event brokers. Also we present the load scheduling algorithm which can achieve load balancing by channel splitting, merging and migration. We conduct the experiments by taking loads with different distributions as input to reveal the capability of dealing with changing loads. The experimental data prove that our mechanism can help balance the system loads efficiently and dynamically start or shut down event brokers when facing overloads or insufficient loads.
[Show abstract][Hide abstract] ABSTRACT: Pub/Sub systems can facilitate monitoring and managing objects for RFID applications. To fully support RFID applications, Pub/Sub systems should provide the means of subscribing RFID tags and the corresponding efficient matching algorithm. This paper provides the management mechanism and matching algorithm for primitive subscriptions whose specification permits to subscribe RFID codes. Our approach organizes clustered subscriptions into a covering forest and then executes primitive subscription matching on the basis of multi-level predicate indexes. Experiments are also conducted to evaluate the performance and overhead of our algorithm.