Design Rules

There are no design rules.

We create software by creating levels of indirection. Design is about having effective ways of manipulating these levels of indirection.

There's no one way of doing this. There are lots of ideas on how to do this. Some ideas are super effective for creating designs that solve certain types of problems but this dosn't mean they will always be the most effective

I think it's therefore a good thinking tool to not categorise oneself as a particular kind of designer, eg "OO", "Functional", "Procedural" etc as it can limit your design choices unnecessarily. I also think categorising your design as "OO" or otherwise can also limit your design options.

This doesn't mean you apply every idea that all the other cool kids are using. Your designs should be reasonably coherent and understandable and not a big messy mish-mash of ideas. Though it does get tricky when you want to introduce new ideas and techniques into an existing system.

So what's my point?

There are no rules. However, coherent and understandable systems tend to have "pseudo" rules. The trick is to not mistake pseudo rules as fundamental rules.