What is a digital library? The issue of definition has been more or less dead now for several years. Not since Howard Besser published his definitional essay in First Monday eight years ago has there been a real serious discussion on how actually to define - and thus make visible – the most novel and innovative library type that we have seen since the emergence of public libraries. Somehow digital libraries are just “there”. But what are they? The library at my university is today approaching a 80 % acquisition rate of digital documents. Only about 20% of what is bought today are printed books and periodicals. Still we hesitate to call this a "digital library". If the same numbers would concern the buying of manuscript, we would most likely talk of a “manuscript library”; if 80% of the acquisition would consist of periodicals, we would talk of a “periodicals library”. Libraries are defined by the character – not just the content – of the documents of which they consist.
When have a library crossed the line between the “traditional” and the digital? Is it even possible to talk of established libraries as digital libraries – or are they something substantially different, and if so, of what does these differences consist?
These questions may seem simple. The answers waiting to be found are intriguingly complex.