Any way to associate a single record of a hasMany?

I was wondering if anyone had ever tried creating an association that links a single record from what would normally be a hasMany association (or knew a clean solution to do so). In this case, I'm working with an article with multiple versions; I'd like to create what is essentially a hasOne relat

$this->passedArgs versus $this->params['named']

In the following case, it appears that both $this->passedArgs and $this->params['named'] will yield the same value from a controller action: /articles/index/date:2009-04-22/page:3 I can't seem to find a clear answer as to whether there is any difference between the two in any situation. Articles