The required id attribute is the QIF id of the measurement resource, used for referencing.
Source
<xs:element name="ProbeTip" type="ProbeTipType"><xs:annotation><xs:documentation>The ProbeTip element is a probe tip.</xs:documentation></xs:annotation></xs:element>
<xs:element name="TipEndLocation" type="PointType"><xs:annotation><xs:documentation>The TipEndLocation element is the location of the point at the end of the tip.</xs:documentation></xs:annotation></xs:element>
<xs:complexType name="LocatedTipType"><xs:annotation><xs:documentation>The LocatedTipType defines a tip of a tactile probe and the location of the end of tip.</xs:documentation></xs:annotation><xs:sequence><xs:element name="ProbeTip" type="ProbeTipType"><xs:annotation><xs:documentation>The ProbeTip element is a probe tip.</xs:documentation></xs:annotation></xs:element><xs:element name="TipEndLocation" type="PointType"><xs:annotation><xs:documentation>The TipEndLocation element is the location of the point at the end of the tip.</xs:documentation></xs:annotation></xs:element></xs:sequence></xs:complexType>