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I was about to send to the PREMIS Editorial Committee this question, having read that part of the Data Dictionary (this question also came up from someone else using PREMIS). I suspect, although am not 100% sure, that it is an error and that we meant to say "If extensions from different external schemas are needed, objectCharacteristicsExtension should also be repeated." It would not make sense to repeat objectCharacteristics as you say, because there are a couple of mandatory elements and it would be redundant. The PREMIS Editorial Committee will try to clarify this and, if necessary, list it as a revision to the Data Dictionary on the PREMIS web site.

Rebecca

Rebecca S. Guenther                                                       
Senior Networking and Standards Specialist                  
Network Development and MARC Standards Office     
Library of Congress   
101 Independence Ave. SE                                                                                      
Washington, DC 20540-4402                                          
(202) 707-5092 (voice)    
(202) 707-0115 (FAX)           
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>>> Robin Wendler <[log in to unmask]> 9/1/2009 10:34 AM >>>
Hi, Ray -- Thanks for responding. you were correct that I had taken this 
off the table because we decided to handle it through a local admin schema 
outside of PREMIS. If we could handle it with PREMIS, so much the better.

The problem I ran into has to do with this instruction in the Data 
Dictionary, specifically the second sentence:

"If objectCharacteristicsExtension container needs to be associated 
explicitly with any PREMIS subunit under objectCharacteristics, the 
container objectCharacteristics is repeated. If extensions from different 
external schemas are needed, objectCharacteristics should also be repeated."

That indicates to me that your perfectly reasonable approach (the example 
of putting MIX and JHOVE output in a single objectCharacteristicsExtension) 
is not allowed.

Does anyone know what that second sentence is meant to accomplish? Having 
to repeat objectCharacteristics in that case means you must also repeat 
required subelements, which is not desirable.

--Robin

At 10:19 AM 9/1/2009 -0400, Ray Denenberg, Library of Congress wrote:
>Robin - First, my apologies for not following up on this sooner.  Your 
>"never mind" message let me to think that you had "withdrawn" the issue 
>(so to speak), but that was probably a faulty assumption, and Rebecca 
>tells me that you are still concerned about this, so let me address it head-on.
>
>I don't think there is necessarily an error either in the dictionary or 
>schema.  That is to say, the schema carries the spirit of the dictionary, 
>which simply says that there may be multiple extensions.  (If you take 
>literally that "objectCharacteristicsExtensions is repeatable" then yes 
>you maintain that there is an error, but I think the "spirit" of the 
>dictionary is that there may be multiple extensions.)
>
>We decided that if you want several extensions within a given 
><objectCharacteristics> element, you should put them all within a single 
><objectCharacteristicsExtension> element, for example:
>
><objectCharacteristicsExtension>
>    <mix:mix xmlns:"http://whatever">
>        <mix:mixelement1></mix:mixelement1>
>        <mix:mixelement2></mix:mixelement2>
>    </mix:mix>
>    <jhove:jhove> xmls:"http://whatever2">
>        <jhove:jhoveelement1></jhove:jhoveelement1>
>        <jhove:jhoveelement2></jhove:jhoveelement2>
>    </jhove:jhove>
></objectCharacteristicsExtension>
>
>This is in contrast to wrapping each extension separately with  an 
><objectCharacteristicsExtension> element, e.g.
>
><objectCharacteristicsExtension>
>    <mix:mix xmlns:"http://whatever">
>        <mix:mixelement1></mix:mixelement1>
>        <mix:mixelement2></mix:mixelement2>
>    </mix:mix>
></objectCharacteristicsExtension>
><objectCharacteristicsExtension>
>    <jhove:jhove> xmls:"http://whatever2">
>        <jhove:jhoveelement1></jhove:jhoveelement1>
>        <jhove:jhoveelement2></jhove:jhoveelement2>
>    </jhove:jhove>
></objectCharacteristicsExtension>
>
>And the latter would have been a perfectly legitimate way to do it, but we 
>didn't want to allow two different ways (to do exactly the same thing) so 
>we chose the first.
>
>However, if the Ed. Board (after seeing this explanation) wants to change 
><objectCharacteristicsExtension>  to repeatable, it can be done very 
>easily in the same manner that we corrected an earlier error (no version 
>change) and I'll be happy to do it.
>
>--Ray
>
>
>
>----- Original Message ----- From: "Robin Wendler" <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Wednesday, August 05, 2009 2:05 PM
>Subject: Re: [PIG] objectCharacteristicsExtension
>
>
>>Never mind. I see the instruction that one must repeat the 
>>objectCharacteristics element to get multiple 
>>objectCharacteristicsExtensions. Don't know why, but I see it. Thanks.
>>
>>At 01:51 PM 8/5/2009 -0400, you wrote:
>>>Hi, all -- Unless I'm missing something (always possible), 
>>>objectCharacteristicsExtension is listed as repeatable in the PREMIS 
>>>Data Dictionary, but it is not repeatable in the 2.0 schema. Can this be 
>>>easily fixed and released, or does it have to wait for the next full iteration?
>>>
>>>Thanks,
>>>--Robin
>>>
>>>
>>>Robin Wendler
>>>Harvard University Library
>>>Office for Information Systems
>>>90 Mt. Auburn St.
>>>Cambridge, MA 02138 USA
>>>617-495-3724 (W)
>>>[log in to unmask]