ISO/IEC 15504, which is known for its process assessment model, was not one of the sources used during the development of the TMMi model. The TMMi model was developed using inputs from sources such as the Capability Maturity Model Integration (CMMI), international testing standards (like those from ISO and IEEE), and industry testing best practices surveys. While the ISO/IEC 15504 model has relevance to general process assessments, it was not specifically referenced in the creation of the TMMi.