The chosen file format is ECXML, for ‘electronics cooling extensible mark-up language’.
“A de facto standard for a number of years, ECXML is now published by JEDEC as the JEP181 guideline,” according to Siemens, which participated in the creation of the standard. “The standard was created to meet a challenge for electronics manufacturers: the absence of a uniform format for the exchange of thermal simulation data throughout supply chains has created unnecessary duplication of effort and the potential introduction of errors into the stream.”
JEP181 was proposed through JEDEC’s JC15 Committee on Thermal Standards.
JEDEC has JEP181 guidelines here (registration required)