Count Element Requirements Class: Basic Types and Simple Components Schemas Requirements Class

SWE Common Data Model OGC 08-094r1 Alternatively it can be used without the value just like any other component.

8.1.7 Quantity Element

The “Quantity” element is the XML schema implementation of the “Quantity” UML class defined in clause 7.2.8. The schema snippet for this element and its corresponding complex type is shown below: element name = Quantity substitutionGroup = swe:AbstractSimpleComponent type = swe:QuantityType complexType name = QuantityType complexContent extension base = swe:AbstractSimpleComponentType sequence element name = uom type = swe:UnitReference element name = constraint maxOccurs = 1 minOccurs = type = swe:AllowedValuesPropertyType element name = value maxOccurs = 1 minOccurs = type = double sequence extension complexContent complexType The “uom” property element is of type “UnitReferencePropertyType” whose complex type definition is given below: complexType name = UnitReference attribute name = code type = swe:UomSymbol use = optional attributeGroup ref = swe:AssociationAttributeGroup complexType This type allows defining a unit of measure by its code using the “code” attribute or by using an “xlink:href” from the “swe:AssociationAttributeGroup” to reference a unit defined externally. Defining the unit of measure by its code expressed using the Unified Code for Units of Measure UCUM is the mandatory way unless the unit cannot be properly expressed with the elements defined in this specification in which case “xlink:href” should be used. Requirement http:www.opengis.netspecSWE2.0reqxsd-simple-componentsucum-code-used Req 64. The UCUM code for a unit of measure shall be used as the value of the “code” XML attribute whenever it can be constructed using the UCUM 1.8 specification. Otherwise the “href” XML attribute shall be used to reference an external unit definition. Constraints can be expressed by using the “AllowedValues” element detailed in clause 8.1.16. The “value” property element takes a decimal value of the XML schema type “double”. This means that special values “–INF”, “INF” and “NaN” for Not a Number are allowed as well as numbers in exponent notation ex: 1.2e-9. Copyright © 2011 Open Geospatial Consortium 75 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 76 Copyright © 2011 Open Geospatial Consortium