Entities can be nested, to form a parent-child relationship. In nested relationship, entities can be nested the way you want using the Xpath node (e.g. /ParentCat/SubCat/SubSubCat/etc). For example, if adding a category called 'SciFi' under an existing category of 'Books', setting the Xpath node to <XPath>/Books/SciFi</XPath> will add the new category as a child of the old one.
On an update, if you want to set a field to NULL or "empty string" use an empty element syntax (e.g. <Summary>string</Summary>).
On an update, if you want to NOT TOUCH the existing value on that field, omit the field from the Xml input document.
Only name field is required. All other fields are optional. ML-encoded data can be included (<ml>....</ml>) to import values in multiple locales at once.
If the XPathLookup attribute is not null, the software will look for the matching entity name & type at that xpath, rather than the root level.
Warnings:
Remember that entities are tied to many other elements within the store. Be fully aware of the changes you're making before doing them.