There are a number of fields that are present in all non-mail folder types. These are:
uid (string, no default)
body (string, default empty)
categories (string, default empty)
creation-date (datetime, no default)
last-modification-date (datetime, no default)
sensitivity (string, default public)
inline-attachment (string, no default)
link-attachment (string, no default)
product-id (string, default empty)
The categories is a comma separated list. There is no fixed set of categories in this format. The clients are free to choose.
The sensitivity possibilites are private, confidential and public.
There can be any number of attachments. "inline-attachment" references the filename of attachments in the mail where this is stored. Attachments not referenced from the XML should simply not be displayed to the user. This allows to attach application-specific attachments (like TNEF for Outlook) that remain hidden to the user.
"link-attachment" means the attachment is external; the contents of the tag is the URL.
The product id is the name of the last application that created or modified the object. It is mostly used for debugging.