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https://issues.apache.org/jira/browse/VALIDATOR-447?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16594870#comment-16594870
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Sebb commented on VALIDATOR-447:
--------------------------------

AFAICT, it's impossible in general to fully validate an ISBN - even with the 
XML file, there will be numbers that don't (yet) correspond with actual 
publications.

Also, the XML file changes frequently (e.g. the attached version (Aug 23) is 
already out of date - there is one dated Aug 28).

Further, it looks as though the HTTP server does not support ETAG or Modified 
timestamps either, so AFAICT one would have to download the full XML file on a 
regular basis.

The code currently detects generic errors such as unexpected prefix and bad 
checksum.
(And AFAIK it does not reject any valid codes - that would obviously be a bug).

What is the use case for stricter validation?
Is there sufficient demand for this to be implemented, documented and 
maintained?

> ISBN style numbers outside ISBN range returning true for isValid
> ----------------------------------------------------------------
>
>                 Key: VALIDATOR-447
>                 URL: https://issues.apache.org/jira/browse/VALIDATOR-447
>             Project: Commons Validator
>          Issue Type: Improvement
>          Components: Routines
>            Reporter: Alex
>            Priority: Major
>              Labels: validators
>         Attachments: RangeMessage.xml
>
>
> All 13 digit EANs with the 979 prefix are validating as ISBNs 
> (ISBNValidator). There are 2 issues with this.
>  # 979-0 prefixed numbers are allocated to the ISMN agency and represent 
> music works. [https://www.ismn-international.org/whatis.html]
>  # 979-[2-9] are unassigned at present, that is they have not yet been 
> allocated to a country agency (or another authority).
> see attached xml (from 
> [www.isbn-international.org/export_rangemessage.xml|http://www.isbn-international.org/export_rangemessage.xml]
>  [^RangeMessage.xml] ) for the current valid ranges for ISBN 
> and 
> [https://en.wikipedia.org/wiki/List_of_ISBN_identifier_groups#Identifiers_of_the_979-_prefix]
> An example unassigned 'ISBN' is 9792222222223



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