Your definition is bunk. We can't cryptographically verify intent for any given transaction, and until that becomes possible you will have to come up with something better.
You asked me about my definition of spam, not how we can limit it by using code.
I also asked why anyone should take your definition seriously.
See, it is not enough to have a definition. Of course you have one, that's unavoidable, even if it is vague and changing over time. But in order for others to care about it, it must be useful in some way. This does not appear to be the case here.