What you're describing is often called "capacity." I found this to be an accessible primer: http://qwafafew.org/images/uploads/san_francisco/sf-20041018-vangeli

What you're describing is often called "capacity." I found this to be an accessible primer: http://qwafafew.org/images/uploads/san_francisco/sf-20041018-vangelisti.pdf http://qwafafew.org/images/uploads/san_francisco/sf-20041018...