Johan,

What is a 'version concept'? I am not sure is it only a casual use of the expression 'concept' instead of 'term' that causes problem - but it may be worth to be more precise...

concept is an idea - this is the level SKOS is supposed to capture by assigning an URI to this idea. New concepts can emerge - semantic field of on concept can split into to or two concepts can be merged to create a new concept. But in principle concepts themselves don't die, disappear, change - so in principle URI is forever. For SKOS two concepts from two different KOS schemes are always two different concepts between which one can state the level of similarity. To what degree two vocabularies speaks of the same concepts can be stated through alignment/mapping - and is defined by the mapping relationship. But even when we state that two concepts means the 'same/equivalent' what is meant is that their semantic fields overlap sufficiently for us to safely operate with them as if they are the same.

Labels are sphere of practical use. Relationship between concepts and terms (labels) is one to many. In real life have to add constraints to the use of labels (preferred term) or change label for practical reasons. Labels (i.e. relationship between concept and label) can become depricated within certain sphere of use and in certain time - but this has nothing to do with the concept itself.

To make it more complicated - in principle in information indexing and retrieval we need to preserve "the knowledge and the history of label/concept relationship" - simply because older recorded documents may have these labels used in the meaning that was relevant for the time when document was created. Good example are geographical and geo-political entities, historical entities such as countries that don't exist anymore, political entities that existed in certain time on which we still have documents. Then also we need to know old and depricated term(s) for entities we now call differently in order to be able to retrieve information on them from the period when they were called differently.

I wonder whether my understanding here is correct - but I certainly don't want to distract Rob and others trying to a good job here.

rgds

Aida