All very sensible, but it makes me wonder (again) what using UML really buys you. I guess if you could write a formal semantics for the diagramming elements you planned to use, it might be possible to generate more sensible code from the diagrams. Steve points out, though, that such a formal semantics clashes with the way people think. And that, I reckon, is the whole problem with UML. In the past (and the present, for some of us) we all used to write whatever gibberish we liked, not necessarily consistently, and it meant whatever we wanted it to mean. Now we have a universal syntax (though no universal semantics), life's a bit different, and diagrams are no longer thoughts written out loud. Now our diagrams have to serve several purposes: to help us clarify design thoughts, to communicate designs to others, to generate stubs, and loads of other stuff. Can one syntax or tool really do all this? I suspect not, and I think Steve's point is the reason why: people don't think unconsciously like they do maths consciously; and that's always been a problem for Computer Science.

The bug is this: for one of my files (and only one) if I type at the command line $ python filename everything works fine, but if I type $ ./filename I get this error message: : No such file or directory and nothing else.

I've tried commenting out the entire file, renaming the file, running cat -v to see if there are odd non-printing characters (there aren't) and now I've run out of ideas :-(