[Standards] Data Forms and empty fields

Brett Zamir brettz9 at yahoo.com
Mon Dec 22 15:28:15 UTC 2008

On 12/22/2008 10:37 PM, Dave Cridland wrote:
> On Mon Dec 22 13:24:25 2008, Brett Zamir wrote:
>> In the Data Forms spec XEP-0004, what is an implementation to do for 
>> each type if there are empty fields?
>> Send an empty<value/>  or an empty<field/>?
>> An empty field would seem to make sense for lists at least, but I 
>> wasn't clear on what it should be for say, text-single.
> <value/> is semantically equivalent to <value></value>, and therefore 
> suggests an actual value of a zero-length string, rather than no value 
> at all.
> Which doesn't answer your question, of course, but it suggests that 
> the answer might depend on what you mean by "empty fields".
Yeah. Or what the spec using Data Forms means (in whether to allow a 
distinction between the two). I think perhaps the specs using Data Forms 
should specify this. For example, in Pubsub, where it is used to send in 
configuration items, perhaps it wouldn't be a bad idea to require 
<value/> to indicate that the sender didn't mistakenly leave out the field.

Otherwise, it is possible one server-side implementation will reject 
data that doesn't at least possess a <value/> child and spit out errors, 
while another may treat an empty <field/> and <field><value/></field> as 
the same, and yet another might spit out errors if there is a <value/> 
child, so I really think this should be specified in the specs using 
Data Forms, if not also mentioned in Data Forms.


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