Perfect or sloppy - RDF, Shirky and Wittgenstein

Danny Ayers picked this one up. Follows Clay Shirky's post on ontologies that I mentioned earlier. Here's the snippet that, I think, ties the linked subject to univers immedia:
It essential[ly] hinges on this, do you believe two people have ever in the history of humanity shared the same (i.e identical) concept. Do you believe that concepts exist as perfect entities that we share or infact do we say a concept is shared when we see a number of people using words in a similar enough way. i.e is the world fuzzz, sloppy and uncertain or is it perfect? Are concepts A Priori or derived?

Quoting further:
This is the essential error that Wittgenstein points out in his later work. There is no single shared meaning that we all can describe in our different ways. To believe so is to believe that a meaning exists A Priori and that language is just our means of describing it. Instead Wittgenstein turns it on its head and says, meaning is nothing more than the way a word is actually used by people.

The post then goes on to describe ways in which his comments are reflected in applications of RDF. Danny Ayers adds a comment to the post which says:
...the vast majority of software in use today is based on similar conceptual approximations, yet somehow manages to be useful.