He was founder and CEO of Object Technology International, which created the products that became IBM VisualAge and eventually Eclipse.
In 1984, Thomas started and led the Object Oriented Research Group at Carleton with colleagues Wilf LaLonde and John Pugh.
[4] Thomas was part of the organizing committees for OOPSLA, ECOOP, and the Danish Java and Object Oriented (JAOO) conferences for many years.
The business was sold to Skills Matter in 2020, and then in 2022 YOW was acquired by Trifork, the organiser of the GOTO conferences in Europe.
[7] Smalltalk With Style Klimas, Edward J., Thomas, David A. and Skublics, Suzanne, Prentice Hall, NJ 1996 ISBN 9780131655492