Bill's format would allow there to be a control field and a data field 
with the same tag, however, so it's all good either way.

Ere Maijala wrote:
> On 03/15/2010 06:22 PM, Houghton,Andrew wrote:
>   
>> Secondly, Bill's specification looses semantics from ISO 2709, as I
>> previously pointed out.  His specification clumps control and data
>> fields into one property named fields. According to ISO 2709, control
>> and data fields have different semantics.  You could have a control
>> field tagged as 001 and a data field tagged as 001 which have
>> different semantics.  MARC-21 has imposed certain rules for
>>     
>
> I won't comment on Bill's proposal, but I'll just say that I don't think 
> you can have a control field and a data field with the same code in a 
> single MARC format. Well, technically it's possible, but in practice 
> everything I've seen relies on rules of the MARC format at hand. You 
> could actually say that ISO 2709 works more like Bill's JSON, and 
> MARCXML is the different one, as in ISO 2709 the directory doesn't 
> separate control and data fields.
>
> --Ere
>
>