<element name="vectorAtStart" type="gml:VectorType">
  <annotation>
    <documentation>"vectorAtStart" is the unit tangent vector at the start point of the spline.</documentation>
  </annotation>
</element>

<element name="vectorAtEnd" type="gml:VectorType">
  <annotation>
    <documentation>"vectorAtEnd" is the unit tangent vector at the end point of the spline.</documentation>
  </annotation>
</element>

<complexType name="CubicSplineRingType">
  <annotation>
    <documentation>the first and last coordinates must be coincident.</documentation>
  </annotation>
  <complexContent>
    <extension base="gml:AbstractRingType">
      <sequence>
        <choice>
          <annotation>
            <documentation>GML supports two different ways to specify the control points of a curve segment. 1. A sequence of "pos" (DirectPositionType) or "pointProperty" (PointPropertyType) elements. "pos" elements are control points that are only part of this curve segment, "pointProperty" elements contain a point that may be referenced from other geometry elements or reference another point defined outside of this curve segment (reuse of existing points). 2. The "posList" element allows for a compact way to specifiy the coordinates of the control points, if all control points are in the same coordinate reference systems and belong to this curve segment only. The number of direct positions in the list must be at least three.</documentation>
          </annotation>
          <choice minOccurs="4" maxOccurs="unbounded">
            <element ref="gml:pos"/>
            <element ref="gml:pointProperty"/>
          </choice>
          <element ref="gml:posList"/>
        </choice>
        <element name="vectorAtStart" type="gml:VectorType">
          <annotation>
            <documentation>"vectorAtStart" is the unit tangent vector at the start point of the spline.</documentation>
          </annotation>
        </element>
        <element name="vectorAtEnd" type="gml:VectorType">
          <annotation>
            <documentation>"vectorAtEnd" is the unit tangent vector at the end point of the spline.</documentation>
          </annotation>
        </element>
      </sequence>
      <attribute name="interpolation" type="gml:CurveInterpolationType" fixed="cubicSpline">
        <annotation>
          <documentation>The attribute "interpolation" specifies the curve interpolation mechanism used for this segment. This mechanism uses the control points and control parameters to determine the position of this curve segment. For a CubicSpline the interpolation is fixed as "cubicSpline".</documentation>
        </annotation>
      </attribute>
      <attribute name="degree" type="integer" fixed="3">
        <annotation>
          <documentation>The degree for a cubic spline is "3".</documentation>
        </annotation>
      </attribute>
    </extension>
  </complexContent>
</complexType>

<attribute name="interpolation" type="gml:CurveInterpolationType" fixed="cubicSpline">
  <annotation>
    <documentation>The attribute "interpolation" specifies the curve interpolation mechanism used for this segment. This mechanism uses the control points and control parameters to determine the position of this curve segment. For a CubicSpline the interpolation is fixed as "cubicSpline".</documentation>
  </annotation>
</attribute>

<attribute name="degree" type="integer" fixed="3">
  <annotation>
    <documentation>The degree for a cubic spline is "3".</documentation>
  </annotation>
</attribute>