[whatwg] Any way to submit only those parts of a form that havechanged?

[dolphinling]

Ian Hickson wrote:
> On Sun, 12 Dec 2004, Ben Meadowcroft wrote:
> 
>>>>I don't feel like doing a detailed readthrough of the spec again 
>>>>(though I did glance at parts that looked relevant), but is there 
>>>>anything in WF2 that allows only parts of a form that have changed 
>>>>from their default value to be submitted?
>>>
>>>There isn't; what would the use case be?
>>
>>Seriously though I recently had to frig this by adding hidden form 
>>elements using Javascript to the form on an onchange handler indicating 
>>when a field had been changed so you don't have to do lookups on the 
>>backend data first to decide if there has been a change or not.
> 
> 
> Be very careful with this -- you should always assume that the 
> client-provided data is hostile, and not trusted.

Once again, if the data's not submitted, it can't be hostile.

> It's quite possible that the field changed while the page was being shown 
> to the user, though, for example if the user loaded the page twice, 
> modified the pages differently, and then submitted both, or if two users 
> did the same thing (unknowingly). 

Collision detection can fix this--and should probably be used anyway, 
since it's just as likely that a collision will mess up the data if all 
fields are submitted.

> (Note that there is also the problem of how to handle checkboxes that I 
> mentioned earlier. Any proposal for how to handle this would have to 
> address that issue first.)

Which problem is this?