Yes, but the downside of your schema is that the distinction between nodes and edges is somewhat muddled. Presumably, all nodes would have nulls in both fromId

Yes, but the downside of your schema is that the distinction between nodes and edges is somewhat muddled. Presumably, all nodes would have nulls in both fromId and toId, but the schema doesn't enforce that. The schema also allows linking edges to other edges. Don't you think this is a bit too much flexibility if the intention is to model a graph?