Sensor Networks’ Integration - Application and Multidisciplinary Aspects of Wireless Sensor Networks - page 104

physical world. Today we observe a tremendous increase of mobile subscribers with
already existing about three billion users of handheld computers. These mobile
devices are powerful communication and computing multipurpose devices that are
increasingly being equipped with a number of different sensors: image, sound, light,
temperature, acceleration, RFID readers, etc. The ability to interact with sensors
in their vicinity via built-in short-range communication interfaces like Bluetooth,
in addition to the previously mentioned characteristics, make mobile devices an
excellent platform for sensing the physical environment and interacting with it. The
authors of CommonSense first analyze the roles of different entities which will
potentially be involved in the provisioning of WSN services in the future, and they
propose the system architecture that incorporates the conclusions of their study.
The first identified entity is the WSN provider who provides the sensor network
its services and because of the equipment ownership, the WSN provider defines
sensor network access and utilization policies. Higher-level services are provided
to the end-users service providers. They combine and process different sensor net-
works services and other required input like Google Maps. The third entity which
provides the link between two aforementioned parties is called CommonSense
provider. It acts as a broker to the service providers and helps them to find a sensor
network, enforces access policies set by individual WSN providers, processes the
data received from multiple sensor networks before delivering these to the requesting
service provider, and provides authentication, accounting, and billing functionality.
The role of the CommonSense provider is to provide a unified interface to services
provided by heterogeneous sensors and actuators. The CommonSense providers
will collaborate with other entities such as location providers, telematics informa-
tion providers, presence providers, etc. These entities, referred to as the third-party
service providers, will process collected information in a specific manner or will be
adding own information to the mix, thus providing additional value to the services
provided by the CommonSense providers.
The CommonSense system is based on a tiered-service-oriented architecture.
The service providers interact with the CommonSense provider, who in turn is the
entity directly interacting with the WSNs. The service providers treat the
CommonSense provider as an entity providing services, and thus have no direct
knowledge or influence over how the CommonSense provider finds the appropriate
data to respond to their requests. This constitutes the first level of the service archi-
tecture. The CommonSense provider then in turn treats the individual WSNs as
entities offering services. This means that the sensor networks have to be able to
describe themselves, where they are, and what they can offer.
Traditionally SOAs focus mainly on peer-to-peer workflow-driven processes. In
CommonSense architecture the authors instead envision that individual, moving
WSNs offer very thin atomic and dynamic services while the CommonSense provider
offers more complex services by combining these primitive WSN services to create
for example mash-ups.
The authors provide several reasons supporting this tiered architecture. The first
is that they wish to create a scalable system where the focus is not on every single
individual sensor, but rather collections of them offering a service. Secondly, focusing