Time and space event model for complex event processing in internet of things in farmland

In internet of things in farmlands, control commands are usually triggered by complex events which contain many dimensionalities of information. Complex events are detected by combining mass of atomic events directly sensed by sensors. That is a typical procedure of complex event processing (CEP). As a basis of CEP, a model of complex events, which describes how atomic events construct complex events, is necessary. Current complex event models focus on temporal logic, but spatial logic relations among farmland events are not considered. In this paper, a novel model that considers both temporal logic and spatial logic was proposed and a relevant XML-based specification language was designed. In the model, multi-level complex events were modeled to a directed graph. For one complex event in the graph, based on analysis of temporal and spatial logic relations among component events, nine time relation operators and eight spatial relation operators were defined to describe above relations; five time combination operators and seven spatial combination operators were defined to calculate attributes of complex events from attributes of atomic events. Based on the model, a XML-based language was defined, which balances readability of users, descriptive abilities and difficulties of parsing and compiling. The proposed event model and language were compared to those used in popular CEP systems e.g. SASE+, Esper, etc. From the comparison, the proposed model and language were more suitable for describing complex events in internet of things in farmlands. © 2015, Chinese Society for Agricultural Machinery. All right reserved.