Database Reference
In-Depth Information
In addition, RFID data exhibits a considerable amount of redundancy
because of multiple scans of the same item, even when it is stationary at
a given location. In practice, one needs to track only interesting move-
ments and activities on the item. The work in [42] proposes methods for
reducing this redundancy. RFID tag readings also exhibit a considerable
amount of
spatial redundancy
because of scans of the same object from
the RFID readers placed in multiple zones. This is primarily because of
the spatial overlap in the range of different sensor readers. This provides
seemingly inconsistent readings because of the inconsistent (virtual) lo-
cations reported by the different sensors scanning the same object. While
the redundancy causes inconsistent readings, it also provides useful in-
formation about the location of an object in cases, where the intended
reader fails to perform its intended function. The work in [28] proposes
a Bayesian inference framework, which takes full advantage of the du-
plicate readings, and the additional background information in order to
maximize the accuracy of RFID data collection.
4.2 Semantic Sensor Web
Sensor networks provide the challenge of too much data, and too lit-
tle inter-operability and also too little knowledge about the ability to
use the different resources which are available in real time. The
Sensor
Web Enablement
initiative of the
Open Geospatial Consortium
defines
service interfaces which enable an interoperable usage of sensor resources
by enabling their discovery, access, tasking, eventing and alerting [21].
Such standardized interfaces are very useful, because such a web hides
the heterogeneity of the underlying sensor network from the applica-
tions that use it. This initiative defines the term
Sensor Web
as an
“infrastructure enabling access to sensor networks and archived sensor
data that can be discovered and accessed using standard protocols and
application programming interfaces.”
This is critical in order to ensure
that the low level sensor details become transparent to application pro-
grammers, who may now use higher level abstractions in order to write
their applications. Clearly, the goal of the sensor web is to enable real
time situation awareness in order to ensure timely responses to a wide
variety of events. The main services and language suite specifications
include the following:
Observations and Measurements (O&M):
Thesearethestandard
models and schema, which are used to encode the real-time mea-
surements from a sensor.
Sensor Model Language (SML):
These models and schema de-
scribe sensor systems and processes. These provide the informa-
