Dennis was the executive editor of Mathematical Reviews as it transitioned from a printed resource to a mainly-digital one.
He graduated from Quanah High School in 1962, and attended Rice University, earning his bachelor's in 1966 and his doctorate in 1970.
[3] He spent the academic year 1970–1971 at the Institute for Advanced Study in Princeton as the first assistant of John Milnor.
[1][4] In 1971, Dennis joined the Department of Mathematics at Cornell University, and he was promoted to full professor in 1981.
[5] During this period Mathematical Reviews designed and began the development of MathSciNet[1][6] which went online in January 1996.