I guess that is exactly where the confusion is at then, the paper:
2.1 Data Format
Dgraph can input data in a JSON format or (slightly modified)
RDF NQuad format. Dgraph would break down a JSON map
into smaller chunks, with each JSON key-value forming one
record equivalent of a single RDF triple record…
A triple is typically expressed as a subject-predicate-object
or a subject-predicate-value. Subject is a node, predicate is a
relationship, and object can be another node or a primitive data
type. One points from a node to another node, the other points
from a node to a value. In the above example, the triple with
name is a type of subject-predicate-value (typically referred
to as an attribute), while the triple with follower is a type of
subject-predicate-object. Dgraph makes no difference in how
it handles these two types of records (to avoid confusion over
these two types, we’ll refer to them as object-values). Dgraph
considers this as the unit of record and a typical JSON map
would be broken into multiple such records.
2.2 Data Storage
Dgraph data is stored in an embeddable key-value database
called Badger [?] for data input-output on disk…
As mentioned above, all records with the same predicate
form one shard. Within a shard, records sharing the same
subject-predicate are grouped and condensed into one single
key-value pair in Badger. This value is referred to as a posting
list, a terminology commonly used in search engines to refer
to a sorted list of doc ids containing a search term. A posting
list is stored as a value in Badger, with the key being derived
from subject and predicate.
I guess I always called it a triple store because of the paper and interpretation of it also by Manish, the founder, in this very forum.
So while it is not a triple store because it stores the subject and predicate concatenated as the key, and the posting list as the value in the KV store, it makes sense to still consider it a triple store in many aspects to understand why it does what it does and how it works under the hood. I think I have a good understanding of Dgraph and much of my understanding is based upon the thought of Dgraph is a triple store.
But you are correct that on the disk there is not a subject-object-predicate as a triple, but rather a “subject-object”-<ordered posting list containing all objects>. So at this point, its just semantics, but I bow to KV.