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

SWE Common Data Model OGC 08-094r1

8.1.5 Category Element

The “Category” element is the XML schema implementation of the “Category” UML class defined in clause 7.2.6. The schema snippet for this element and its corresponding complex type is shown below: element name = Category substitutionGroup = swe:AbstractSimpleComponent type = swe:CategoryType complexType name = CategoryType complexContent extension base = swe:AbstractSimpleComponentType sequence element name = codeSpace maxOccurs = 1 minOccurs = type = swe:Reference element name = constraint maxOccurs = 1 minOccurs = type = swe:AllowedTokensPropertyType element name = value maxOccurs = 1 minOccurs = type = string sequence extension complexContent complexType The “codeSpace” element is of type “swe:Reference” and thus makes use of an “xlink:href” XML attribute to reference an external dictionary, taxonomy or ontology representing the code space Please refer to the documentation of the “xlink:simpleLink” attribute group for more details. Constraints can be expressed by using the “AllowedTokens” element detailed in clause 8.1.15. The “value” property element is of the XML schema type “string”. The text content of this element should however be limited to short tokens in the case of a categorical representation. The following example shows how the “codeSpace” element can be used to give the value of a geological period: swe:Category definition = http:sweet.jpl.nasa.gov2.0timeGeologic.owlGeologicTime swe:label Geological Period swe:label swe:description Name of the geological period according to the nomenclature of the International Commission on Stratigraphy swe:description swe:codeSpace xlink:href = http:sweet.jpl.nasa.gov2.0timeGeologic.owlPeriod swe:value Jurassic swe:value swe:Category Note that the code space references an existing dictionary defined by CGI Commission for the Management and Application of Geoscience Information. This shows how SWE Common can leverage an existing community managed terminology. Alternatively it can be used without the value to describe, for instance, a “bird species” field in a biology dataset: swe:Category definition = http:sweet.jpl.nasa.gov2.0biol.owlSpecies swe:label Bird Species swe:label swe:description Bird species according to the classification of the World Bird Database swe:description swe:codeSpace xlink:href = http:www.birdlife.orgdatazonespeciesindex.html swe:Category Copyright © 2011 Open Geospatial Consortium 73 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 74 Copyright © 2011 Open Geospatial Consortium