Dear Colleagues, There are two new research reports available on coalgebras and languages (regular and context-free): A Bialgebraic Review of Regular Expressions, Deterministic Automata and Languages By Bart Jacobs http://www.cs.ru.nl/research/reports/info/NIII-R05003.html Context-free Languages via Coalgebraic Trace Semantics By Ichiro Hasuo, Bart Jacobs http://www.cs.ru.nl/research/reports/info/NIII-R05004.html Best wishes, Bart.