Hi everybody, I haven't been reading this list for a while but now I have a question people on categories may have thought about. May be trivial... apologies in advance. A strict monoidal category is a monoidal one where all the isos are indentities, e.g. we have that A(x)(B(x)C) = (A(x)B)(x)C and also f(x)(g(x)h) = (f(x)g)(x)H because the natural iso is the identity. A nice example is the skeletal cat of finite sets, i.e. objects are natural numbers and Hom m n = {i<m} -> {i<n}. This cat is even strictly bimonoidal with + and *. However, even though both operators are symmetric and A(x)B = B(x)A we don't have f(x)g = g(x) f - hence I wouldn't call this one strictly symmetric monoidal. Are there any (constructive) examples of non-trivial strict symmetric monoidal cats? I am thinking about reversible computations and quantum, btw. Cheers, Thorsten This message has been checked for viruses but the contents of an attachment may still contain software viruses, which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation.