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The Translucent Approach



To perform positioning system integration and control it is necessary to manage several low-level details. As instance, how many and which positioning systems are currently available, which information positioning systems provide, how it is possible to control them. Take into consideration an LBS which wants to minimize power consumption. First of all, it has to contact each positioning system requesting for their power consumption, then it must deactivate most consuming positioning systems. Moreover, LBS has to periodically monitor positioning system power consumption since it may change over the time. Obviously, it is not possible to pretend LBSs are able to interact with integrated positioning systems so deeply.

We propose a middleware solution to integrate positioning systems and easily control them from the application level. A middleware solution to dynamically integrate and control positioning systems must manage a wide range of low level details, most of them known only at service provisioning time. The middleware can provide those information to the application level or not. Depending on detail amount provided to applications, the middleware approach is closer to two opposite ones: transparent and visible.

  • The traditional transparent approach tries to hide every low level implementation details to minimize complexity a LBS must manage, without any possibility to interact directly with lower levels. This approach is helpful to easily and rapidly deploy LBSs which only need standard and static information about exploited services, i.e. positioning systems. Most of contributions presented in Section 2 follow this approach. However in a dynamic research field, as positioning is, it is hard to have a priori knowledge of which features a positioning system is able to offer, which capabilities have and which details an application is interested in.
  • On the contrary, a visible approach gives the capability to interact with positioning systems directly, but rising LBS deployment complexity, since LBSs must manage complexity derived from positioning system integration and control.

Translucent logo.

PoSIM is based on a translucent approach which adopts both transparent and visible approaches. Briefly, the translucent approach is achieved with a cross-layering architecture where LBSs are allowed to interact either in a high- or low-level abstraction fashion. In particular, not only components with distant abstraction levels are allowed to interact each other, but also LBSs are allowed to interact with every middleware component, both high- and low-level ones.

Thanks to the translucent approach, PoSIM is able to suit the following two principles:
  1. it is possible to provide both high and low level details, satisfying simple and smart application requirements;
  2. it is possible to control lower abstraction level components from the application level, either in a transparent or visible manner for respectively simple and smart applications.
In fact translucent approach achieves a twofold goal. On the one hand, simple applications are able to get location information and control positioning systems through high abstraction middleware components. PoSIM provides to simple LBSs, that is without any or few low level detail knowledge, a way to request high level abstraction behaviors, e.g., a particular location information model or power consumption level, regardless how many and which positioning systems are actually exploited. On the other hand, smart LBSs are able to interact with positioning systems directly, through a uniformed positioning system description, but without hiding any peculiarity, to make easier the interaction with newly added, a priori unknown positioning systems.

Let us stress thanks to the transparent approach PoSIM provides two fundamental capabilities. First of all, it provides the integration of new, a priori unknown positioning systems in a completely dynamic, plug-in fashion. Then, it allows the control of newly added positioning systems, through specific interfaces provided from positioning system developers. Exploiting PoSIM, LBSs are able to take advantage from and even control every newly integrated positioning system, even if not known both at service deployment and provisioning time. In fact, LBSs do not interact with positioning systems directly, but through their description, known only at run-time.

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