The REST API documentation doesn’t have any method to read from a data extension while it has a couple of writing into it.
So is SOAP is the only API to read from a DE?
It’s not documented save for a call to
GET https://www.exacttargetapis.com/data/v1/rest, but
GET https://www.exacttargetapis.com/data/v1/customobjectdata/key/[DE CustomerKey]/rowset/ will do exactly what you want, and it’s not limited to data extensions linked to the contact model.
I’ve also found it will accept at least the same query string parameters as the ContentBuilder simple asset query plus
$top. You can build more complex filters with
OR, and parentheses.
Property IS [NOT] NULL works too.