The person behind [[Post production systems]] is [[Emil Leon Post]], an American mathematician and logician. Born in Augustow, Poland, in 1897, Post immigrated to the United States with his family when he was young. He made significant contributions to the field of mathematical logic and the foundations of computer science. ### Biography and Contributions - **Education and Early Career**: Emil Post received his Ph.D. from Columbia University in 1920, where he wrote a dissertation on an extension of a fundamental theorem of classical invariant theory under the supervision of Cassius Keyser. After obtaining his degree, Post encountered difficulties in securing a teaching position, partly due to the after-effects of World War I and also due to his partial physical disability stemming from a childhood accident. - **Contributions to Mathematical Logic and Computation**: Post is best known for his work on what are now called [[Post production systems]], which are a type of rewriting system that laid foundational concepts in the theory of formal languages. He also developed the Post Correspondence Problem, an undecidable decision problem that was a significant contribution to the theory of computation. Post's work was foundational in the development of the field of recursive function theory, a branch of mathematical logic that deals with functions that can be computed by a logical or mathematical procedure. ### Post’s Canonical and Normal Forms - Post explored various systems of rules and their corresponding generative capacities, which led to the development of what are now termed as Post canonical and normal forms. These systems provide a framework for understanding various computational processes and have influenced the development of programming languages and algorithms. ### Legacy - **Influence on Turing and Computability Theory**: Post's ideas and the conceptual machinery he developed were contemporaneous and, in some aspects, prescient of the work of [[Alan Turing]]. Post's model of computation and his formulation of what it means for a function to be computable laid groundwork that paralleled and sometimes anticipated Turing's work on the [[Turing Machine]], a fundamental model of computation that underlies computer science. - **Post's Later Work**: In his later years, Post returned to the subjects of completeness and consistency in mathematical systems, working on problems of undecidability and the properties of recursively enumerable sets, which are key concepts in logic and computer science. Emil Post passed away in 1954, but his legacy endures in the ongoing development of theoretical computer science, where his innovations continue to influence new generations of thinkers and technologies. His work on formal systems, particularly Post production systems, has proved critical in the advancement of understanding how languages and computations can be formally analyzed and processed. # References ```dataview Table title as Title, authors as Authors where contains(subject, "Emil Leon Post") sort modified desc, authors, title ```