FollowTrajectory action: trajectory or catalogReference
The description of the "FollowTrajectory Action" reads:
The trajectory can be instantiated from a catalog type, or defined within this declaration.
However, the XSD Schema is the following
<xsd:complexType name="FollowTrajectoryAction">
<xsd:all>
<xsd:element name="Trajectory" type="Trajectory" minOccurs="0"/>
<xsd:element name="CatalogReference" type="CatalogReference" minOccurs="0"/>
<xsd:element name="TimeReference" type="TimeReference"/>
<xsd:element name="TrajectoryFollowingMode" type="TrajectoryFollowingMode"/>
</xsd:all>
</xsd:complexType>
meaning that the FollowTrajectoryAction can have a Trajectory child element AND a CatalogReference.
To express the definition that the trajectory shall be instantiated either from a catalog reference or from within the declaration, I would suggest the following:
<xsd:choice>
<xsd:element name="Trajectory" type="Trajectory"/>
<xsd:element name="CatalogReference" type="CatalogReference"/>
</xsd:choice>