OGC 08-094r1 SWE Common Data Model
In this example, no official code space URI was found so the “codeSpace” element is used to reference the online source of the taxonomy The “birdlife.org” website hosts the
international database that is the reference in this case.
When no code space is specified, Req 25 must be satisfied by inserting a constraint with a list of allowed values as shown in the example below:
swe:Category definition
= http:www.opengis.netdefpropertyOGC0SensorStatus
swe:label Sensor Status
swe:label swe:description
Current status of the sensor swe:description
swe:constraint swe:AllowedTokens
swe:value Off
swe:value swe:value
Stand-by swe:value
swe:value Ready
swe:value swe:value
Busy swe:value
swe:AllowedTokens swe:constraint
swe:Category
Note that in this case, the data consumer has no way of knowing the exact meaning of each allowed value, since there is no associated description. A code space is thus more
explicit as it defines not only the list of allowed terms but should also give a textual description. This is why a code space is preferred whenever it is possible to implement it.
8.1.6 Count Element
The “Count” element is the XML schema implementation of the “Count” UML class defined in clause 7.2.7. The schema snippet for this element and its corresponding
complex type is shown below:
element name
= Count
substitutionGroup =
swe:AbstractSimpleComponent type
= swe:CountType
complexType name
= CountType
complexContent extension
base =
swe:AbstractSimpleComponentType sequence
element name
= constraint
maxOccurs =
1 minOccurs
= type
= swe:AllowedValuesPropertyType
element name
= value
maxOccurs =
1 minOccurs
= type
= integer
sequence extension
complexContent complexType
Constraints are expressed by using the “AllowedValues” element detailed in clause 8.1.16. The “value” property element is of the XML schema type “integer”.
The following example shows how this XML element can be used to give the value of a geological period:
swe:Count definition
= http:www.opengis.netdefpropertyOGC0NumberOfPixels
swe:label Row Size
swe:label swe:description
Number of pixels in each row of the image swe:description
swe:value 1024
swe:value swe:Count
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Copyright © 2011 Open Geospatial Consortium
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
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