Seems like I am having a bunch of JSF related questions these days... here it goes again: why does AJAX call declared with f:ajax post all the fields of the form and not only those declared with execute? This question was already asked in the Sun forums, but as they are now closed I cannot reply there. The thread there is a stub with no real answer to this.
What's the point of submitting all the form fields if I need to use only some of them?
I am not 100% sure, but this might be a bug in Mojarra. See a similar question about the special @all keyword.
In short: Mojarra doesn't obey the list of forms entered for execute attribute of f:ajax but always submits only the enclosing form. The same probably applies to a more detailed field level as well - Mojarra does not obey the execute attribute when choosing what fields to submit, but simply sends them all. It does obey the execute attribute when processing the data in the server-side, however.
Can anyone test if the behavior differs from this with Apache Myfaces?