Why are edges required in a Relay/GraphQL Connection?

Question

In a Relay/GraphQL schema configuration, one-to-many relationships (with pagination) are specified as in the tutorial example

type ShipConnection {
  edges: [ShipEdge]
  pageInfo: PageInfo!
}
type ShipEdge {
  cursor: String!
  node: Ship
}

However, the one-to-one connection made by ShipEdge seems redundant. Why can't we move the cursor to ShipConnection and store an array of Ship IDs as edges?

type ShipConnection {
  edges: [Ship]
  pageInfo: PageInfo!
  cursor: String!
}

What were the design decisions to require one extra object for every edge in a one-to-many relationship?

Answer 1

The edges field provides you with a place to put per-edge data. For example, you might want to put a creator or priority field on there, describing who added the edge and how important the relationship is, respectively.

If you don't require this kind of flexibility (or the other features that you get with connections, such as pagination), you could use a simple GraphQLList type. See this answer for more on the difference between between connections and lists.