I think one popular name, independent of the format, is to call them documents. Or more specifically, the type of database which use them often runs under that term. Maybe specify it as data-document to not confuse it with freeform office-documents.

But one problem is, that each format has slightly different ways it works. Some have nodes which support properties, some not. This makes building a proper query-language a bit more complicated if it should not end up ugly.