5.2.3 Overview of the SWE Architecture
From Geostandards
5 Sensor Web Enablement
5.1 Scope of the course
5.2 Introduction to SWE
- 5.2.1 Sensor Networks
- 5.2.2 What is Sensor Web Enablement?
- 5.2.3 Overview of the SWE Architecture
- 5.2.4 Benefits of SWE
- 5.4.1 Sensor Observation Service
- 5.4.2 Sensor Planning Service
- 5.4.3 Sensor Alert Service
- 5.4.4 Sensor Discovery
Contents |
SWE building blocks
The SWE architecture comprises of two major blocks:
- the information model consists of the underlying conceptual models and encodings, and
- the services model is the specification of services.
The separation into these two blocks represetns a logical view point on the SWE architecture, but does not imply that there are no links between both block.
Information model overview
The information model comprises of the several specifications in which the conceptual model of the SWE architecture is defined. Further on, these specifications define an XML encoding to be used for information exchange by means of the services model. The basic concepts are:
- Transducers represent the interface between the real and the digital world; Transducers that translate phenomenon to data are typically referred to as sensors, and transducers that translate data to phenomenon are called transmitters or actuators.
- A (sensor) system transforms one or more inputs based on a given methodology to one or more outputs. It consists of a set of transducers, for which the relative positions to an internal coordinate system is defined. By relating the internal coordinate system to a geographic reference system, the system, its components as well as the produced measurements can be georeferenced.
- An observation is the act of observing a phenomenon.It contains information
concerning the lineage of the measurement, the resulting value, time of measurement, and the observed phenomenon.
The amount of information contained by the above mentioned elements increases from raw data (transducer) to processed data (observation). Each logical layer of the information model forms the basis of another layer. Applications have access to all of these layers, but they should use the information of the higher layers to guarantee a higher level of interoperability.
The information model is build up by the following specifications:
- SWE Common - common encoding for basic data types used in all SWE specifications
- Observations and Measurements Schema (O&M) – standard models and XML Schema for encoding observations and measurements from a sensor, both archived and real-time
- Sensor Model Language (SensorML) – standard models and XML Schema for describing sensors systems and processes; provides information needed for discovery of sensors, location of sensor observations, processing of low-level sensor observations, and listing taskable properties
- Transducer Model Language (TransducerML) – Conceptual approach and XML Schema for supporting real-time streaming of data to and from sensor systems
Services model overview
Within the services model the services of the SWE architecture are described. The SWE services are the following ones:
- Sensor Observations Service (SOS) – standard web service interface for requesting, filtering, and retrieving observations and sensor system information
- Sensor Planning Service (SPS) – standard web service interface for requesting user-driven acquisitions and observations, to (re-)calibrate a sensor or to task a sensor network
- Sensor Alert Service (SAS) – standard web service interface for publishing and sub-scribing to alerts from sensors
- Web Notification Services (WNS) – standard web service interface for asynchronous delivery of messages or alerts from any other web service
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