[Auscope-geosciml] An issue with ISO DataQuality and UnitsOfMeasure schema [SEC=UNCLASSIFIED]

[Oliver.Raymond at ga.gov.au]

Hi all,

I have discovered a quirk/bug in the ISO DataQuality UML model and schemas that we should be aware of, but should not be a show-stopper for us using ISO DataQuality.

According to the ISO19115 UML model (see diagram below), gmd:DQ_QuantitativeAttributeAccuracy/result/DQ_QuantitativeResult/valueUnit is of type gco:UnitOfMeasure (imported from ISO 19103).

[cid:image001.jpg at 01CA4B64.E67C0260]


However, contrary to the above UML diagram, the ISO19139 XML schema implementation (gco/basicTypes.xsd) actually imports UnitOfMeasure from GML (ISO 19136), not from ISO 19103.  As a result, the attributes of DQ_QuantitativeResult/valueUnit that appear in the XML schema are quite different to those shown in the ISO 19115 UML diagram.

Snippet from gml/units.xsd....

  <element name="unitOfMeasure" type="gml:UnitOfMeasureType">
    <annotation>
      <documentation>The element gml:unitOfMeasure is a property element to refer to a unit of measure. This is an empty element which carries a reference to a unit of measure definition.</documentation>
    </annotation>
  </element>
  <complexType name="UnitOfMeasureType">
    <sequence/>
    <attribute name="uom" type="gml:UomIdentifier" use="required"/>
  </complexType>
  <element name="UnitDefinition" type="gml:UnitDefinitionType" substitutionGroup="gml:Definition">
    <annotation>
      <documentation>A gml:UnitDefinition is a general definition of a unit of measure. This generic element is used only for units for which no relationship with other units or units systems is known.
The content model of gml:UnitDefinition adds three additional properties to gml:Definition, gml:quantityType, gml:quantityTypeReference and gml:catalogSymbol.
The gml:catalogSymbol property optionally gives the short symbol used for this unit. This element is usually used when the relationship of this unit to other units or units systems is unknown.</documentation>
    </annotation>
  </element>
  <complexType name="UnitDefinitionType">
    <complexContent>
      <extension base="gml:DefinitionType">
        <sequence>
          <element ref="gml:quantityType" minOccurs="0"/>
          <element ref="gml:quantityTypeReference" minOccurs="0"/>
          <element ref="gml:catalogSymbol" minOccurs="0"/>
        </sequence>
      </extension>
    </complexContent>
  </complexType>

 UML diagram of the GML UnitDefinition class from ISO 19136:

[cid:image002.jpg at 01CA4B64.E67C0260]


My colleague John Hockaday is contacting the lead author of ISO 19139 to find out why the schema and the ISO 19115 UML don't match.

Cheers,
Ollie

------------------------------------------------------------------------------------------------
Ollie Raymond
National Advice,  Maps and Standards Project
Geoscience Australia

Address: GPO Box 378, Canberra, ACT, 2601, Australia | ABN: 80 091 799 039
Ph: (02) 62499575 | Fax: (02) 62499992 | Email: Oliver.Raymond at ga.gov.au
Web:  http://www.ga.gov.au/minerals/research/national/nat_maps/nat_geol_maps.jsp<http://www.ga.gov.au/geoscience/national>

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