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===== SensorWeaver =====
SensorWeaver is a suite of applications that enables application development in distributed sensor networks scenarios.
It comprises:
  * A Middleware Platform for secure communications between applications and sensor network gateway nodes
  * Applications that leverage Middleware functionalities

The software project is licensed with Apache V2 licensing.

This page collects developers and administrators documentation on SensorWeaver components.

===== Middleware =====

Wireless Sensor networks are often heterogeneous in terms of communication technologies and protocols and cover a limited spatial area. Applications that use sensor data needs are often run remotely and require a secure communication channel in order to access it over the Internet.
SensorWeaver Middleware tries to address the aforementioned issues by offering simple abstractions and API to clients and a distributed platform for secure communication between sensor nodes and applications that use context data.

{{ ::componentdiagram.jpg|Sample deployment diagram depicting a scenario with ZigBee devices integration}}

The functionalities offered by the Middleware are based on the simple //datafeed// and //service// abstractions. A //datafeed// generally identifies an entity that produces data and can be characterized with a set of properties and a message content definition.
There are two areas of functionalities concerning the datafeeds, one for data publishers and one for data consumers: 
  * Datafeed publishing and sensor data dissemination
    * Announce the presence of a new datafeed by providing a description in terms of sensor properties and message format
    * Announce unavailability of a datafeed
    * Publish data for a published datafeed, using the defined message format
  * Datafeed discovery and data listening
    * Discover datafeeds matching a set of properties
    * Listening for data produced by a datafeed

Regarding the services, the following functionalities for both the publishers and the consumers are provided:
  * Service publishing
    * Announce the presence of a new service by providing a description of the properties, request message format and response message format
    * Announce unavailability of a service
    * Reply to a service invocation from a client
  * Service discovery and invocation
    * Discover services matching a set of properties
    * Invoking a service and receiving a response

Any data source can be represented as a //data feed// on the middleware, enabling a sensor data fusion scenario.

The deployment diagram depicts a scenario where ZigBee devices are integrated with the Middleware. 
In this case a Gateway computing node runs an OSGi container with several components. The //Sensor publisher// component realizes the integration layer by relying on a technology specific software stack (ZB4O for ZigBee sensor networks) in order to access the sensor network. The stack uses a physical dongle in order to access the ZigBee network. //Sensor publisher// monitors the status of the sensor network and, for each discovered sensor, publishes the availability and generated sensor data on the //Middleware//.
The //Middleware// relies on MQTT communications in order to propagate information to interested nodes in a distributed environment.
//Applications// running on other physical nodes can be notified in real time about the availability of new data sources and listen to data generated by those.

The Middleware does not offer off-the-shelf integration layers for specific sensor communication technologies (Bluetooth, ZigBee, Z-Wave, etc.) or virtual sensor representations ([[https://github.com/osgi/design/raw/master/rfcs/rfc0196/rfc-0196-DeviceAbstractionLayer.pdf|OSGi rfc0196]], [[http://zb4osgi.aaloa.org/|ZB4O]], etc.).

Main characteristics:
  * Runs on Java and OSGi execution environment
  * Leverage MQTT publish/subscribe messaging protocol on the lower level
  * Underlying publish/subscribe communication paradigm based of MQTT protocol
  * based on modern IoT communication protocol on the lower level: MQTT
  * Provides secure communication channels
  * Offers a simple model for the description/discovery of data sources
  * Strives for simplicity of integration

Links to guides:
  *[[sensorweaver:developer-guide|SensorWeaver Developer Guide]]
  *[[sensorweaver:admin-guide|SensorWeaver Administrator Guide]]
  *[[sensorweaver:sensor-feeds|SensorWeaver The Sensor Feeds]]