John Ross Quinlan is a computer science researcher in data mining and decision theory.
Quinlan is a specialist in artificial intelligence, particularly in the aspect involving machine learning and its application to data mining.
[2] Ross Quinlan invented the Iterative Dichotomiser 3 (ID3) algorithm which is used to generate decision trees.
C5.0, which Quinlan is commercially selling (single-threaded version is distributed under the terms of the GNU General Public License), is an improvement on C4.5.
The advantages are speed (several orders of magnitude faster), memory efficiency, smaller decision trees, boosting (more accuracy), ability to weight different attributes, and winnowing (reducing noise).