Stephen Downes has an interesting article on Meaning, Use, and Metadata:

In my view, the massive efforts underway to tag, to carefully sort, classify and describe, learning object metadata is misplaced. It is misplaced not because t is wrong or misleading (though that possibility is certainly built in by assumption). It is misplaced because such metadata descriptions can, at best, represent only one point of view of the description and the application of a learning object.

We will not be able to approach the usefulness contained in the promise of learning objects - and of the semantic web more generally - until we get past this idea that we can define it (and in passing, all of human knowledge), a priori. We can't. The very best we can do is establish (through, say, RDF) relations between intended meaning of terms. But at some point, we need to step back and observe how these entities are being used, and to capture that as our definitive metadata.

Someone quotes a passage from Alice in Wonderland in the followup comments:

''There's glory for you!'

'I don't know what you mean by 'glory',' Alice said.

Humpty Dumpty smiled contemptuously. 'Of course you don't -- till I tell you. I meant 'there's a nice knock-down argument for you!''

'But 'glory' doesn't mean 'a nice knock-down argument',' Alice objected.

'When I use a word,' Humpty Dumpty said, in rather a scornful tone, 'it means just what I choose it to mean -- neither more nor less.'

'The question is,' said Alice, 'whether you can make words mean so many different things.'

'The question is,' said Humpty Dumpty, 'which is to be master -- that's all.' '