Semantic language has it's limits and rightfully so. The point of communication (sometimes) is to add something new. New things by definition have no pre-defined category. Therefore some content can only be described by inventing something. It's a moving target. I guess some attempt is a good thing like having a <title> tag, but it will never be perfect and if some day it is perfect then we are a dead species. I sincerely hope that most data continues to defy description.