Basic Data Types Requirements Class: Basic Types and Simple Components Packages Requirements Class
SWE Common Data Model OGC 08-094r1
The “extension” attribute is used as a container for future extensions. Each extension should put its content in a separate extension property. It is available by inheritance to all
sub-classes of “AbstractSWEValue”. This extension point can be used at runtime i.e. at the instance level in the case of XML encoding to add new extended properties to an
existing class.
The optional “name” and “description” attributes can be used to provide human readable information describing what property the component represents. The “name” is meant to
hold a short descriptive name whereas “description” can carry any length of plain text. These two fields should not be used to specify robust semantic information see 6.3.1.
Instead, the “definition” attribute described below should be used for that purpose.
The optional “identifier” attribute allows assigning a unique identifier to the component, so that it can be referenced later on. It can be used, for example, when defining the
unique identifier of a universal constant.
The “definition” attribute identifies the property often an observed property in our context that the data component represents by using a scoped name. It should map to a
controlled term defined in an web accessible dictionary, registry or ontology. Such terms provide the formal textual definition agreed upon by one or more communities,
eventually illustrated by pictures and diagrams as well as additional semantic information such as relationships to units and other concepts, ontological mappings, etc.
Examples
The definition may indicate that the value represents an atmospheric temperature using a URN such as “urn:ogc:def:property:OGC::SamplingTime” referencing the complete definition in a register.
The definition may also be a URL linking to a concept defined in an ontology such as “httpwww.opengis.netdefOGC0SamplingTime”
The name could be “Sampling Time”, which allows quick identification by human data consumers. The description could be “Time at which the observation was made as measured by the on-board clock” which adds
contextual details.
The “optional” attribute is an optional flag indicating if the component value can be omitted in the data stream. It is only meaningful if the component is used as a schema
descriptor i.e. not for a component containing an inline value. It is ‘false’ by default.
The “updatable” attribute is an optional flag indicating if the component value is fixed or can be updated. It is only applicable if the data component is used to define the input of a
process i.e. when used to define the input or parameter of a service, process or sensor, but not when used to define the content of a dataset.
Examples
The “updatable” flag can be used to identify what parameters of a system are changeable. The exact semantics depends on the context. For example:
Copyright © 2011 Open Geospatial Consortium
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OGC 08-094r1 SWE Common Data Model
- In SensorML process chains, the “updatable” flag is used to identify process parameters that can accept an incoming connection and thus can get changed while the process is in execution.
- In a SensorML System it is used to indicate whether or not a system parameter is changeable, either by an operator i.e. by turning a screw or inserting a jumper or remotely by sending a command.
- In the Sensor Planning Service it is used to indicate if tasking parameters are changeable by the client i.e. by using the Update operation after a task has been submitted.