OGC 08-094r1 SWE Common Data Model
The following example shows how this XML element can be used to wrap a continuous measurement value. In this case, a temperature measurement with a value of 21.5°C is
shown:
swe:Quantity definition
= http:sweet.jpl.nasa.gov2.0physThermo.owlTemperature
swe:label Outside Temperature
swe:label swe:description
Outside temperature taken at the top of the antenna swe:description
swe:uom code
= Cel
swe:value 21.5
swe:value swe:Quantity
The following example illustrates the use of a more complex UCUM unit for a radiance measurement The value is 0.0283 watts per square meter per steradian per micrometer:
swe:Quantity definition
= http:sweet.jpl.nasa.gov2.0physRadiation.owlSpectralRadiance
swe:label Radiance
swe:label swe:description
Radiance measured on band1 swe:description
swe:uom code
= W.m-2.Sr-1.um-1
swe:value2.83 e-2
swe:value swe:Quantity
The “Quantity” element is also often used to define projected quantities. For example, it can be used to define the altitude of a plane with respect to a well defined vertical
reference system:
swe:Quantity definition
= http:sweet.jpl.nasa.gov2.0spaceExtent.owlHeight
referenceFrame =
http:www.opengis.netdefcrsEPSG05714 axisID
= H
swe:label MSL Height
swe:label swe:description
Height above mean sea level swe:description
swe:uom code
= m
swe:value 1320
swe:value swe:Quantity
The “referenceFrame” attribute is used here to reference a well know vertical coordinate reference system unambiguously defined in the EPSG database. This example means that
the height is measured along the H axis of the EPSG reference system code 5714 Mean Sea Level Height, and has a value of 1320 meters.
Like in any other data component the “value” property element can be omitted when this element is used as a data descriptor for a field which value is provided separately.
8.1.8 Time Element
The “Time” element is the XML schema implementation of the “Time” UML class defined in clause 7.2.9. The schema snippet for this element and its corresponding
complex type is shown below:
element name
= Time
substitutionGroup =
swe:AbstractSimpleComponent type
= swe:TimeType
complexType name
= TimeType
complexContent extension
base =
swe:AbstractSimpleComponentType sequence
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SWE Common Data Model OGC 08-094r1
element name
= uom
type =
swe:UnitReference element
name =
constraint maxOccurs
= 1
minOccurs =
type =
swe:AllowedTimesPropertyType element
maxOccurs =
1 minOccurs
= name
= value
type =
swe:TimePosition sequence
attribute name
= referenceTime
type =
dateTime use
= optional
attribute name
= localFrame
type =
anyURI use
= optional
extension complexContent
complexType
The “uom” property element is of type “UnitReferencePropertyType”. It has the same requirements as its equivalent in the “Quantity” element. When ISO 8601 calendar
notation is used, it is specified as a unit by using a special value in the “xlink:href” attribute i.e. for simplicity, a calendar representation is considered here as a complex
unit composed of year, month, day, hours, minutes and seconds.
Requirement
http:www.opengis.netspecSWE2.0reqxsd-simple-componentsiso8601-uom-used
Req 65. When ISO 8601 notation is used to express the measurement value
associated to a “Time” element, the URI “http:www.opengis.netdefuomISO‐
86010Gregorian” shall be used as the value of the “xlink:href” XML attribute on
the “uom” element.
Additional constraints on the value can be expressed by using the “AllowedTimes” element detailed in clause 8.1.17. The “value” property element takes either a decimal
value or a calendar value encoded according to the ISO 8601 standard. This is enforced by using the “TimePosition” simple type defined below as the union of the “double” and
“TimeIso8601” data types:
simpleType name
= TimePosition
union memberTypes
= double swe:TimeIso8601
simpleType simpleType
name =
TimeIso8601 union
memberTypes =
date time dateTime swe:TimeIndeterminateValue simpleType
simpleType name
= TimeIndeterminateValue
restriction base
= string
enumeration value
= now
restriction simpleType
The “double” data type is used to express time as a scalar decimal number i.e. a duration and can be any of the special values “-INF”, “INF” and “NaN” just like the
value of a “Quantity” component.
The “date”, “time” and “dateTime” data types are built-in types of XML Schema and are implemented according to ISO 8601 complete representations of date, time and
combination of date and time respectively see XML schema 1.0 specification and ISO 8601 for details on the format.
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