On 8/5/14, 3:13 AM, Juha Hakala wrote:
>> Sadly especially libraries took their part in blurring that semantics,
>> but that is a different story.
> Can you elaborate a bit what you mean by this? 

Thomas may be referring to the usage in the MARC format:

*$a - International Standard Book Number*

Valid ISBN. /ISBN/ and the embedded hyphens may be generated for display.

*020* 	*##**$a*0491001304

As you can see, the hyphens are removed, and the ISBN is a single string 
of 0-9,X. "Valid ISBN" there does not refer to the form (e.g. removed 
hyphens) but to the fact that there is another subfield for ISBNs that 
have either been assigned to the MARC or that appear on the actual book 
that have later turned out to be invalid in some way (re-used, typo'd, etc.)


Karen Coyle
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