(2nd try, took my gloves off...) Hello Café, I have been fascinated by Cat. theory for quite a few years now, as most people who get close to it I think. I am a developer, working mostly in Java for my living and dabbling with haskell and scala in my spare time and assuming the frustration of having to live in an imperative word. More often than not, I find myself trying to use constructs from FP in my code, mostly simple closures and typical data types (eg. Maybe, Either...). I have read with a lot of interest FPS (http://homepages.mcs.vuw.ac.nz/~tk/fps/) which exposes a number of OO patterns inspired by FP. Are there works/thesis/books/articles/blogs that try to use Cat. theory explicitly as a tool/language for designing software (not as an underlying formalisation or semantics)? Is the question even meaningful? Thanks in advance, Arnaud