Recently I was wondering what the difference between the "Local" and "Remote" settings in the "Run mode" property of a form part actually meant. I couldn't find any documentation on the wiki.
In a Microsoft Yammer community Harold Albrich of terna GmbH pointed me to an earlier answer in the same forum. Since this blog also serves as my own notebook, I'll share my version of the answer here:
When the form part is called as Remote, there is no coupling between the form part and the caller form. So no linking of data sources and also no element.caller() object. And as Remote the form part is executed in a separate session.
With Local it is the other way around. You can link data sources and you can work with element.caller().