[Developers] Casting ISBN-10 to ISBN-13

[Richard Newman]

> We are thinking about standardizing on 13-digit ISBNs for the  
> property /book/book_edition/ISBN on the Book Edition type. To  
> accomplish this, all ISBN-10s (~60K of them) would have to be  
> converted to ISBN-13s. These new ISBN-13s would then completely  
> replace the old ISBN-10s.

If you regard the ISBN as being an attribute shared by instances of  
the edition, then I'd suggest having separate ISBN-10 and ISBN-13  
properties, because you want to preserve the value printed on the  
book. A user searching by the number on the book won't know to  
translate their ISBN-10 to ISBN-13; a book with both fields printed on  
the dust jacket (despite a well-documented 1-1 mapping) should perhaps  
have both properties.

Standardizing on ISBN-13 also means you can't draw interesting graphs  
of the gradual uptake of ISBN-13 by querying on the existence of each  
property over publication time :)


> 2) /book/book_edition/ISBN is not currently unique. This should  
> probably be a unique property. That is to say, multiple book  
> editions can have the same ISBN but individual book editions should  
> not have multiple ISBNs.

 From experience in the book industry: don't count on anything about  
ISBNs being correct other than their checksums :)

Assuming that each book has one ISBN is probably fair (until you find  
otherwise), but definitely don't assume that it's an inverse  
functional property (ISBNs have been known to be reallocated).

Consider that the same edition might be issued in different  
territories with different ISBNs, even in the same language. Is it the  
same edition? That's a semantic question.

-R