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

Oliver.Raymond at ga.gov.au Oliver.Raymond at ga.gov.au
Mon Oct 12 17:41:02 EDT 2009


Hmm, it just makes it difficult for us poor souls who are trying to use the ISO UML to model our data when it doesn't accurately reflect what will be delivered by the xml schema....



________________________________
From: auscope-geosciml-bounces at lists.arcs.org.au [mailto:auscope-geosciml-bounces at lists.arcs.org.au] On Behalf Of Simon Cox
Sent: Monday, 12 October 2009 7:50 PM
To: auscope-geosciml at lists.arcs.org.au
Cc: Hockaday John
Subject: Re: [Auscope-geosciml] An issue with ISO DataQuality and UnitsOfMeasure schema [SEC=UNCLASSIFIED]

Ollie - Its all OK.

You have to distinguish between the abstract model and the implementation.

Sometimes they are related by a rule (e.g. the 19136 Annex E, or 19139 encoding rule), but sometimes they are just related by a 'mapping', particularly if there is a pre-existing implementation that captures the semantics.
Thats what has happened in this case.

It is also explained in Annex D of ISO 19136 (GML) where the GML implementations of classes from ISO 19103 are explained.

Simon


--------------------------------------------------------
Simon Cox

European Commission, Joint Research Centre
Institute for Environment and Sustainability
Spatial Data Infrastructures Unit, TP 262
Via E. Fermi, 2749, I-21027 Ispra (VA), Italy
Tel: +39 0332 78 3652
Fax: +39 0332 78 6325
mailto:simon.cox at jrc.ec.europa.eu
http://ies.jrc.ec.europa.eu/simon-cox

SDI Unit: http://sdi.jrc.ec.europa.eu/
IES Institute: http://ies.jrc.ec.europa.eu/
JRC: http://www.jrc.ec.europa.eu/

--------------------------------------------------------



________________________________
From: auscope-geosciml-bounces at lists.arcs.org.au [mailto:auscope-geosciml-bounces at lists.arcs.org.au] On Behalf Of Oliver.Raymond at ga.gov.au
Sent: Monday, 12 October 2009 08:53
To: auscope-geosciml at lists.arcs.org.au
Subject: [Auscope-geosciml] An issue with ISO DataQuality and UnitsOfMeasure schema [SEC=UNCLASSIFIED]

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:385073621 at 12102009-1991]


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:385073621 at 12102009-1998]


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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