_:alice <mobile> "040123456" (since=2006-01-02T15:04:05) .
Is ‘since’ a predicates? Does it need to be defined in advance? Or add directly to the rdf data？
No, since is a Facet. Facets are extra info that you add in an Edge (value or connection). See https://dgraph.io/docs/query-language/facets/
As facets aren’t a first-class citizen, you don’t need to define them on the schema.
What types of ‘facets’ support, will he recognize them automatically?
I moved the binary file to another server, why the schema still exists
I have deleted p, w, zw files
Yes, it will.