OGC 08-094r1 SWE Common Data Model
Requirement
http:www.opengis.netspecSWE2.0requml-simple-componentstime-range-valid
Req 33. All requirements associated to the “Time” class defined in clause 7.2.9
apply to the “TimeRange” class.
The “value” attribute of the “TimeRange” class takes a pair of values of type “TimePosition” representing the inclusive minimum and maximum bounds of the extent.
7.2.15 Quality Union
The “Quality” class is a union allowing the use of different representations of quality. Quality can be indeed be specified as a decimal value, an interval, a categorical value or a
textual statement. In our model, quality objects are in fact data components used in a recursive way, as shown on the following diagram:
«Union»
Quality
«property» + byQuantity:
Quantity + byQuantityRange: QuantityRange
+ byCategory: Category + byText: Text
Figure 7.18 – Quality Union
These different representations of quality are useful to cover most use cases where simple quality information is provided with the data.
Examples
“Quantity” is used to specify quality as a decimal number such as accuracy, variance and mean, or probability. “QuantityRange” is used to specify a bounded interval of variation such as a bi-directional tolerance.
“Category” is used for a quality statement based on a well defined taxonomy such as certification levels. “Text” is used to include a textual quality statement such as a comment written by a field operator.
The “definition” attribute of the chosen quality component helps to further define the type of quality information given just like any other data component, and the “uom” should be
specified in the case of a decimal quality value or interval.
Note: Reusing data components to specify quality also allows the inclusion of quality values in the data stream itself. This is useful if the quality is varying and re-estimated for
each measurement. This is for example the case in a GPS receiver where both horizontal
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SWE Common Data Model OGC 08-094r1
and vertical errors are given along with the geographic position. See the XML implementation clause for more information on this use case.
7.2.16 NilValues Class
The “NilValues” class is used by all classes deriving from “AbstractSimpleComponent”. It allows the specification of one or more reserved values that may be included in a data
stream when the normal measurement value is not available see clause 6.4.2. The UML model of this class is given below:
«Type»
NilValues
«DataType»
Basic Types::NilValue
«property» +nilValue
1.. «property»
+ reason: ScopedName + value: CharacterString
Figure 7.19 – NilValues Class
An instance of the “NilValues” class is composed of one to many “NilValue” objects, each of which specifies a mapping between a reserved value and a reason.
The mandatory “reason” attribute indicates the reason why a measurement value is not available. It is a resolvable reference to a controlled term that provides the formal textual
definition of this reason usually agreed upon by one or more communities.
Requirement
http:www.opengis.netspecSWE2.0requml-simple-componentsnil-reason-resolvable
Req 34. The “reason” attribute of an instance of the “NilValue” class shall map to
the complete human readable definition of the reason associated with the NIL
value.
The mandatory “value” attribute specifies the data value that would be found in the stream to indicate that a measurement value is missing for the corresponding reason. The
range of values allowed here is the range of values allowed by the datatype of the parent data component.
Copyright © 2011 Open Geospatial Consortium
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