On August 27, 1858, Italian mathematician and philosopher Giuseppe Peano was born. He is he author of over 200 books and papers, and is considered the founder of mathematical logic and set theory. The standard axiomatization of the natural numbers is named the Peano axioms in his honor. These axioms have been used nearly unchanged in a number of metamathematical investigations, including research into fundamental questions of consistency and completeness of number theory.
Looking for interesting data sets? Here's a list of more than 100 of the best stuff, from dolphin relationships to political campaign donations to death row prisoners.
One of my collegaues called the other day and asked if we still relied on the distinction between intensional and extensional sets (really intensionally and extensionally defined sets). Yes, even more so now.
R. Agrawal, T. Imielinski, and A. Swami. SIGMOD '93: Proceedings of the 1993 ACM SIGMOD international conference on Management of data, page 207--216. New York, NY, USA, ACM Press, (1993)
M. Bezem, T. Coquand, and S. Huber. 19th International Conference on Types for Proofs and Programs (TYPES 2013), volume 26 of Leibniz International Proceedings in Informatics (LIPIcs), page 107--128. Dagstuhl, Germany, Schloss Dagstuhl--Leibniz-Zentrum fuer Informatik, (2014)