Current documentation at https://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/lexical/IfcTendon.htm
indicates:

A tendon is a steel element such as a wire, cable, bar, rod, or strand used to impart prestress to concrete when the element is tensioned.

NOTE Definition according to ISO 6707-1: steel bar(s) or groups of bars, strands or wires given a tensile stress that produces a compressive stress in prestressed concrete or masonry.

In reality "tensioning" is a "pre-" or "post-" process. Can the language be edited to... "... impart compressive strength to concrete when the element is given a tensile stress (prestressed or post-tensioned)."? This would help align with the ISO definition and cover both cases.