In 1962 Schmidt began work at TU München with students of Robert Sauer, in the beginning in labs and tutorials, later in mentoring and administration. Schmidt's interests turned toward programming when he collaborated with Hans Langmaack on rewriting and the braid group in 1969. Friedrich L. Bauer and Klaus Samelson were establishing software engineering at the university and Schmidt joined their group in 1974. In 1977 he submitted his Habilitation "Programs as partial graphs".[1]
He became a professor in 1980. Shortly after that, he was appointed to hold the chair of the late Klaus Samelson for one and a half years. From 1988 until his retirement in 2004, he held a professorship at the Faculty for Computer Science of the Universität der Bundeswehr München. He was a classroom instructor for beginners courses as well as special courses in mathematical logic, semantics of programming languages, construction of compilers, and algorithmic languages. Working with Thomas Strohlein, he authored a textbook on relations and graphs, published in German in 1989 and English in 1993 and again in 2012.
In 2001 he became involved in a large project (17 nations) with the European Cooperation in Science and Technology:[2] Schmidt was chairman of project COST 274 TARSKI (Theory and Application of Relational Structures as Knowledge Instruments).[3]
In 2014 a festschrift was organized to celebrate his 75th year.[4]
The calculus of relations had a relatively low profile among mathematical topics in the twentieth century, but Schmidt and others have raised that profile. The partial order of binary relations can be organized by grouping through closure. In 2018 Schmidt and Michael Winter published Relational Topology which reviews classical mathematical structures, such as binary operations and topological space, through the lens of calculus of relations.
2003: (with de Swart, H. C. M., Orłowska, E., and Roubens, M.) Theory and Application of Relational Structures as Knowledge Instruments, Kickoff volume of the COST Action 274: TARSKI, Lecture Notes in Computer Science #2929, Springer, ISBN3-540-20780-5
2001: (with Parnas, D., Kahl, W.)[8] Relational Methods in Software, Special Issue of Electronic Notes in Theoretical Computer Science,, vol. 44, numbers 3, ISSN1571-0661
1999: (with Jaoua, A.)[9] Relational Methods in Computer Science, Special Issue of Information Sciences, vol. 119, numbers 3+4, Elsevier
1991: (with Berghammer, R.) Graph-Theoretic Concepts in Computer Science, vol. 570 of Lecture Notes in Computer Science, Proc. 17th Intern. Workshop WG '91, Jun 17-19, Richterheim Fischbachau, Springer 1991, ISBN3-540-55121-2, ISBN0-387-55121-2
1987: (with Tinhofer, G)[10]Graph-Theoretic Concepts in Computer Science vol. 246 of Lecture Notes in Computer Science, Proc. 12th Intern. Workshop WG '86, Jun 17–19, Kloster Bernried, Springer, ISBN3-540-17218-1, ISBN0-387-17218-1
1982: (with Broy, M.) Theoretical Foundations of Programming Methodology. Reidel Publishers, ISBN90-277-1460-6.
1981: (with Bauer, F. L.) Erinnerungen an Robert Sauer, Beiträge zum Gedächtniskolloquium anläßlich seines 10. Todestages, Springer