Spontaneous task composition in urban computing environments based on social, spatial, and temporal aspects

Ubiquitous and urban computing share the goal of enabling users to access networked services and resources anytime, anywhere. The intermesh of planned and situational activities is a distinguishable characteristic of urban computing environments. This produces a diversity of service requirements that need to be tackled by opportunistically suggesting appropriate services to users or social groups, without having a previous definition of applications in templates or any other descriptions in advance. This paper leverages the approach of task-oriented computing to represent user goals in tasks. A task is composed of unit-tasks: user centric configurations of abstract service coordinations. The focus of this paper is on the provision of a mechanism to cover the spontaneous unit-task composition cycle, based on social, spatial, and temporal aspects. This is realized by identifying the essential semantic elements that describe unit-tasks, UrbComp environments, and social groups. We have extended a unit-task selection mechanism from our previous work. In addition, this paper contributes a set of composability metrics based on social, spatial, and temporal aspects. These metrics concern the measurement of semantic interoperability and potential conflicts between unit-tasks or unit-task composites. These metrics are used to join unit-tasks together in sequences. Experimental results for a real dataset of tasks were obtained. These results show a suitable time-overhead for the unit-task selection mechanism. In addition, a simulation of arrivals at a crowded space was utilized to measure the performance, throughput, and efficacy ratio of the composition mechanism.