interface as well as how to execute the model. It also precisely defines its own inputs, outputs and parameters. Process Chain - Composite non-physical processing block consisting of interconnected sub-processes, which can in turn be Process Models or Process Chains. A process chain also includes possible data sources as well as connections that explicitly link input and output signals of sub-processes together. It also precisely defines its own inputs, outputs and parameters. Process Method - Definition of the behavior and interface of a Process Model. It can be stored in a library so that it can be reused by different Process Model instances (by using 'xlink' mechanism). It essentially describes the process interface and algorithm, and can point the user to existing implementations. Detector - Atomic component of a composite Measurement System defining sampling and response characteristic of a simple detection device. A detector has only one input and one output, both being scalar quantities. More complex Sensors such as a frame camera which are composed of multiple detectors can be described as a detector group or array using a System or Sensor. In SensorML a detector is a particular type of Process Model. Sensor - Specific type of System representing a complete Sensor. This could be for example a complete airborne scanner which includes several Detectors (one for each band). How did it come about? In 1998, under the auspices of the international Committee for Earth Observing Satellites (CEOS), Dr. Mike Botts began development of an XML-based Sensor Model Language for describing the geometric, dynamic, and radiometric properties of dynamic remote sensors. Initial development was funded under a NASA AIST Program, and in 2000, SensorML was brought under the oversight of the Open Geospatial Consortium (OGC) where it served as a catalyst for the OGC Sensor Web Enablement (SWE) initiative. SensorML design has benefited greatly from the interactions of members of the OGC Sensor Web Enablement Working Group. The continued development of SensorML has been supported by the Interoperability Program of OGC, as well as the US Environmental Protection Agency (EPA), the US National GeoSpatial-Intelligence Agency (NGA), the US Joint Interoperability Test Command (JITC), the US Defense Information Systems Agency (DISA), SAIC, General Dynamics, Northrop Grumman, Oak Ridge National Labs, and NASA. See also Observations and Measurements Semantic Sensor Web IEEE 1451 Transducer electronic data sheet Sensor Grid External links SensorML page at OGC Open Geospatial Consortium homepage OGC