In the sensor network area, BSNs encompass a particular set of restrictions and conditions that separate them from normal WSNs. More so than WSNs, BSNs would profit from different types of sensing information and the sensor network itself provides more opportunities for different applications to use the same resources. However, the heterogeneity of sensor HW devices and the myriad of different applications that try to use them are an obstacle to its development. A problem is the need to address specific characteristics of the HW without abstractions that 1) provide the freedom to access the needed information while 2) complying to a set of requirements and 3) optimizing resource usage according to a set of metrics. We propose a middleware approach for abstracting lower level details from applications. We enrich the approach by building models in the middle layer fed with data from the sensor network and query-able from the application layer. Furthermore: a) applications should be able to set requirements to be met in providing the information, b) several applications should be able to share the same resources, c) the resources should be optimized so as to meet the requirements and prolong the lifetime of the BSN.