From IFWiki

The virtual machine model that forms the cornerstone of TADS 3. It was created in 1999 by Michael J. Roberts to replace the aging TADS virtual machine, which was hampered by considerations for hardware that is no longer in use and lacked modern features like garbage collection, exception handling, and Unicode.

The T3 VM specification is somewhat behind actual development as of the time of writing (4 September 2005), but remains the official reference for those implementing ports of the T3 VM and/or software that needs to work with the T3 story file format.