Sensor web is a type of sensor network that heavily utilizes the World Wide Web and is especially suited for environmental monitoring.
OGC's Sensor Web Enablement (SWE) framework defines a suite of web service interfaces and communication protocols abstracting from the heterogeneity of sensor (network) communication.
Definition
The term "sensor web" was first used by Kevin Delin of NASA in 1997,
As a result, on-the-fly data fusion, such as false-positive identification and plume tracking, can occur within the sensor web itself and the system subsequently reacts as a coordinated, collective whole to the incoming data stream. For example, instead of having uncoordinated smoke detectors, a sensor web can react as a single, spatially dispersed, fire locator.
The term "sensor web" has also morphed into sometimes being associated with an additional layer connecting sensors to the World Wide Web.
The Sensor Web Enablement (SWE) initiative of the Open Geospatial Consortium (OGC) defines service interfaces which enable an interoperable usage of sensor resources by enabling their discovery, access, tasking, as well as eventing and alerting. By defining standardized service interfaces, a sensor web based on SWE services hides the heterogeneity of an underlying sensor network, its communication details and various hardware components, from the applications built on top of it.
OGC's SWE 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. Through this abstraction from sensor details, their usage in applications is facilitated.
Characteristics of Delin's sensor web architecture
Delin designed a sensor web as a web of interconnected pods. All pods in a sensor web are equivalent in hardware (there are no special "gateway" or "slave" pods). Nevertheless, there are additional functions that pods can perform besides participating in the general sensor web function. Any pod of a sensor web can be a portal pod and provides users access to the sensor web (both input and output).
Access can be provided by RF modem, cell phone connections, laptop connections, or even an Internet server. In some cases, a pod will have an attached removable memory unit (such as a USB stick or a laptop) that stores collected data. Often the mother pod serves as a primary portal point to the Internet, but this is done only for deployment convenience. Early papers referenced the mother pod as "a prime node" if it additionally contained special hardware for a particular type of input/output device (say an RF modem).
Because of the inherent hopping of data within a sensor web, a pod with no attached sensors can be deployed as a relay with the single purpose of facilitating communication between the other pods and to expand the communication range to a particular end-point (such as a mother pod).
The number of pods may vary, with examples of sensor webs with 12 to 30 pods.
Sensor webs consisting of pods have been deployed that have spanned miles and run continuously for years.
Sensor webs have been fielded in harsh environments (including deserts, mountain snowpacks, and Antarctica)
for the purposes of environmental science and have also proved valuable in urban search and rescue and infrastructure protection.
The technology is not only monitoring the environment but sometimes also controlling the environment by actuating devices.