The correct key to use is “uid” in order to the XIDS and mapping to work.
e.g:
{
"uid" : "_:00004178-a951-4425-a260-40e548189169",
"author_id" : "00004178-a951-4425-a260-40e548189169",
"full_name" : "Joe Johnson",
"dgraph.type" : "Author"
}
{
"uid" : "_:d6d30b03-27cf-4156-8b63-0218ff69a2bc",
"book_id" : "d6d30b03-27cf-4156-8b63-0218ff69a2bc",
"title" : "Awesome Book Title",
"date" : "2018-10-11",
"dgraph.type" : "Book"
}
and then
{
"uid": "_:00004178-a951-4425-a260-40e548189169",
"authored": {
"uid": "_:d6d30b03-27cf-4156-8b63-0218ff69a2bc"
}
}