Research On Dynamic Task Model And Information Interactive Mode For Location Based Services

In task model there is not only the knowledge on management of context but also the knowledge on solutions of practical problems. Current task modeling of LBS is still unable to meet the requirements on diversity of objectives, sharing of information and efficiency of operations as the complex context elements are always involved in LBS and the objective in task could be changed under way.A framework of dynamic task model, named DAMo, is proposed in the thesis based on an analysis of characteristics in task model of LBS. In DAMo there are two aspects of improvement for existing task model, one is to enhance description capability of task model on dynamic multi-tasks and the other is to improve description capability of task model on information transmission. Three concepts are applied in the DAMo model. (1) Task type: Descriptions of task attributes and approach to implement it. (2) Task operations: Descriptions of the relationship in multi-tasks, including as insert, replace, link, unify and suspend. (3) Task channel: Descriptions of information transmission. Each type of operation corresponds to a kind of channel, which describes the interrelation of attribute values of tasks that participate in the operations. It is convenient to describe the dynamic changing, composition, and information interaction of task using the three concepts mentioned above.To improve the running efficiency of DAMo, the extended tuple space is adopted as the mode of information interaction in the middleware of LBS. As a distributed communication mechanism, the tuple space is capable to process heterogeneous, asynchronous and loosely coupled information interaction. It always needs to extend the concept of tuple space for special requirements in applications as the traditional concepts are too simple. The concept of interactive channel is introduced in ChaSpace which is an extended tuple space. The channel is a point-to-point communication media which has a specific ID and two different interactive terminals. A channel can act as an independent communication agent in collaborative system to ensure the non-coupling of time and space in communication. The combination of tuple space and channel model will make up a unique collaborative interactive model, which can be used for both the information sharing of tuple space and the operation controlling of channel. The model provides direct support for information interaction in DAMo through tuple template, filtering rule and triggering rule. In a case study, DAMo is employed in describing task model of a digital museum guide system. Research results demonstrate that DAMo can be used to effectively describe information interaction in multi-tasks of LBS.