The optional turned attribute shows if the arc is inverted. A value of 1 (or true) means the arc is inverted. A value of 0 (or false) means the arc is not inverted.
Source
<xs:element name="ArcCircular12Core" type="ArcCircular12CoreType" substitutionGroup="Curve12Core"><xs:annotation><xs:documentation>The global ArcCircular12Core element is the mathematical core of a 2D circular arc.</xs:documentation></xs:annotation></xs:element>