# GMLAS - Mapping examples

This page gives a few examples of how XML constructs are mapped to OGR layers and fields by the GMLAS - Geography Markup Language (GML) driven by application schemas driver.

Mapping examples
Schema | Document | OGR layers | Comments
--- | --- | --- | ---
    <schema xmlns="http://www.w3.org/2001/XMLSchema">
    <element name="MyFeature">
    <complexType>
        <sequence>
            <element name="name" type="string"/>
        </sequence>
        <attribute name="id" type="ID" use="required"/>
        <attribute name="attr" type="string"/>
    </complexType>
    </element>
    </schema>
    <MyFeature id="my_id" attr="attr_value">
        <name>my_name</name>
    </MyFeature>
    Layer name: MyFeature
    Geometry: None
    id: String (0.0) NOT NULL
    attr: String (0.0)
    name: String (0.0) NOT NULL
    OGRFeature(MyFeature):1
        id (String) = my_id
        attr (String) = attr_value
        name (String) = my_name
| Element with attributes and sub-elements of simple type and maximum cardinality of 1.
    <schema xmlns="http://www.w3.org/2001/XMLSchema">
    <element name="MyFeature">
    <complexType>
        <sequence>
            <element name="str_array" type="string"
                    maxOccurs="2"/>
            <element name="dt_array" type="dateTime"
                    maxOccurs="unbounded"/>
        </sequence>
        <attribute name="id" type="ID" use="required"/>
    </complexType>
    </element>
    </schema>
    <MyFeature id="my_id">
        <str_array>first string</str_array>
        <str_array>second string</str_array>
        <dt_array>2016-09-24T15:31:00Z</dt_array>
        <dt_array>2016-09-24T15:32:00Z</dt_array>
    </MyFeature>
    Layer name: MyFeature
    Geometry: None
    id: String (0.0) NOT NULL
    str_array: StringList (0.0) NOT NULL
    OGRFeature(MyFeature):1
        id (String) = my_id
        str_array (StringList) =
            (2:first string,second string)

    Layer name: MyFeature_dt_array
    Geometry: None
    ogr_pkid: String (0.0) NOT NULL
    parent_id: String (0.0) NOT NULL
    value: DateTime (0.0)
    OGRFeature(MyFeature_dt_array):1
        ogr_pkid (String) = my_id_dt_array_1
        parent_id (String) = my_id
        value (DateTime) = 2016/09/24 15:31:00+00

    OGRFeature(MyFeature_dt_array):2
        ogr_pkid (String) = my_id_dt_array_2
        parent_id (String) = my_id
        value (DateTime) = 2016/09/24 15:32:00+00
| Example with array and child layer
    <schema xmlns="http://www.w3.org/2001/XMLSchema">
    <element name="MyFeature">
    <complexType>
        <sequence>
        <element name="identifier">
            <complexType>
            <sequence>
                <element name="name">
                <complexType>
                    <simpleContent>
                    <extension base="string">
                        <attribute name="lang"
                                type="string"/>
                    </extension>
                    </simpleContent>
                </complexType>
                </element>
                <element name="namespace" type="string"
                        minOccurs="0"/>
            </sequence>
            </complexType>
        </element>
        </sequence>
        <attribute name="id" type="ID" use="required"/>
    </complexType>
    </element>
    </schema>
    <MyFeature id="my_id">
        <identifier>
            <name lang="en">my_name</name>
            <namespace>baz</namespace>
        </identifier>
    </MyFeature>
    Layer name: MyFeature
    Geometry: None
    id: String (0.0) NOT NULL
    identifier_name_lang: String (0.0)
    identifier_name: String (0.0)
    identifier_namespace: String (0.0)
    OGRFeature(MyFeature):1
        id (String) = my_id
        identifier_name_lang (String) = en
        identifier_name (String) = my_name
        identifier_namespace (String) = baz
| Example of nested element, that can be folded into main layer. Use of an attribute on a sub-element.
    <schema xmlns:myns="http://myns"
            targetNamespace="http://myns"
            elementFormDefault="qualified"
            xmlns="http://www.w3.org/2001/XMLSchema">

    <element name="AbstractFeature" abstract="true"/>

    <element name="FeatureCollection">
    <complexType><sequence>
        <element ref="myns:AbstractFeature" maxOccurs="unbounded"/>
    </sequence></complexType>
    </element>

    <complexType name="namesType">
    <sequence>
        <element ref="myns:name" maxOccurs="unbounded"/>
    </sequence>
    </complexType>

    <element name="MyFeature" substitutionGroup="myns:AbstractFeature">
    <complexType><sequence>
        <element name="names" type="myns:namesType"/>
        </sequence>
        <attribute name="id" type="ID" use="required"/>
    </complexType>
    </element>

    <element name="MyFeature2" substitutionGroup="myns:AbstractFeature">
    <complexType><sequence>
        <element name="names" type="myns:namesType"/>
        </sequence>
        <attribute name="id" type="ID" use="required"/>
    </complexType>
    </element>

    <element name="name">
    <complexType><sequence>
        <element name="name" type="string"/>
        <element name="lang" type="string"/>
    </sequence></complexType>
    </element>

    </schema>
    <FeatureCollection xmlns="http://myns">
        <MyFeature id="my_id">
            <names>
                <name>
                <name>name</name>
                <lang>en</lang>
                </name>
                <name>
                <name>nom</name>
                <lang>fr</lang>
                </name>
            </names>
        </MyFeature>
        <MyFeature2 id="my_id2">
            <names>
                <name>
                <name>nom2</name>
                <lang>fr</lang>
                </name>
            </names>
        </MyFeature2>
    </FeatureCollection>
    Layer name: name
    OGRFeature(name):1
        ogr_pkid (String) = _name_1
        name (String) = name
        lang (String) = en

    OGRFeature(name):2
        ogr_pkid (String) = _name_2
        name (String) = nom
        lang (String) = fr

    OGRFeature(name):3
        ogr_pkid (String) = _name_3
        name (String) = nom2
        lang (String) = fr

    Layer name: MyFeature
    OGRFeature(MyFeature):1
        id (String) = my_id

    Layer name: MyFeature2
    OGRFeature(MyFeature2):1
        id (String) = my_id2

    Layer name: MyFeature_names_name_name
    OGRFeature(MyFeature_names_name_name):1
        occurrence (Integer) = 1
        parent_pkid (String) = my_id
        child_pkid (String) = _name_1

    OGRFeature(MyFeature_names_name_name):2
        occurrence (Integer) = 2
        parent_pkid (String) = my_id
        child_pkid (String) = _name_2

    Layer name: MyFeature2_names_name_name
    OGRFeature(MyFeature2_names_name_name):1
        occurrence (Integer) = 1
        parent_pkid (String) = my_id2
        child_pkid (String) = _name_3
| Example of of a common element "name" referenced by 2 layers "MyFeature" and "MyFeature1". The links are established through the junction layers "MyFeature_names_name_name" and "MyFeature2_names_name_name".

## swe:DataArray

The following snippet

    <swe:DataArray>
        <swe:elementCount>
            <swe:Count>
                    <swe:value>2</swe:value>
            </swe:Count>
        </swe:elementCount>
        <swe:elementType name="Components">
            <swe:DataRecord>
                    <swe:field name="myTime">
                        <swe:Time definition="http://www.opengis.net/def/property/OGC/0/SamplingTime">
                                <swe:uom xlink:href="http://www.opengis.net/def/uom/ISO-8601/0/Gregorian"/>
                        </swe:Time>
                    </swe:field>
                    <swe:field name="myCategory">
                        <swe:Category definition="http://dd.eionet.europa.eu/vocabulary/aq/observationverification"/>
                    </swe:field>
                        <swe:field name="myQuantity">
                        <swe:Quantity definition="http://dd.eionet.europa.eu/vocabulary/aq/primaryObservation/hour">
                                <swe:uom xlink:href="http://dd.eionet.europa.eu/vocabulary/uom/concentration/ug.m-3"/>
                        </swe:Quantity>
                    </swe:field>
                    <swe:field name="myCount">
                        <swe:Count definition="http://"/>
                    </swe:field>
                        <swe:field name="myText">
                        <swe:Text definition="http://"/>
                    </swe:field>
                        <swe:field name="myBoolean">
                        <swe:Boolean definition="http://"/>
                    </swe:field>
            </swe:DataRecord>
        </swe:elementType>
        <swe:encoding>
                <swe:TextEncoding decimalSeparator="." blockSeparator="@@" tokenSeparator=","/>
        </swe:encoding>
        <swe:values>2016-09-01T00:00:00+01:00,1,2.34,3,foo,true@@2017-09-01T00:00:00,2,3.45</swe:values>
    </swe:DataArray>

will receive a special processing to be mapped into a dedicated layer:

    Layer name: dataarray_1_components
    Geometry: None
    Feature Count: 2
    Layer SRS WKT:
    (unknown)
    parent_ogr_pkid: String (0.0) NOT NULL
    mytime: DateTime (0.0)
    mycategory: String (0.0)
    myquantity: Real (0.0)
    mycount: Integer (0.0)
    mytext: String (0.0)
    myboolean: Integer(Boolean) (0.0)
    OGRFeature(dataarray_1_components):1
      parent_ogr_pkid (String) = BAE8440FC4563A80D2AB1860A47AA0A3_DataArray_1
      mytime (DateTime) = 2016/09/01 00:00:00+01
      mycategory (String) = 1
      myquantity (Real) = 2.34
      mycount (Integer) = 3
      mytext (String) = foo
      myboolean (Integer(Boolean)) = 1

    OGRFeature(dataarray_1_components):2
      parent_ogr_pkid (String) = BAE8440FC4563A80D2AB1860A47AA0A3_DataArray_1
      mytime (DateTime) = 2017/09/01 00:00:00
      mycategory (String) = 2
      myquantity (Real) = 3.45

## See Also

- main documentation page for GMLAS driver