Representing a graph in JSON

json-ld was made for this. It has a semi-steep learning curve, but it is a robust way to represent graph data in json.

Turns out there are standards that are trying to emerge for this sort of thing. I recently had to look these up for a project of my own. You might be interested in http://jsongraphformat.info/ for example, or one of the peer projects it references on its website. Goals include trying to represent in JSON anything you can represent in the DOT language (https://en.wikipedia.org/wiki/DOT_(graph_description_language)).

Since the DAG's edges hold data, they better have their own identifiers, just like the nodes. That is, the json representation should be composed of three components:

1. Node records: mapping each node identifier to the node's data.
2. Edge records: mapping each edge identifier to the edge's data.

3. Adjacency lists: mapping each node identifier to an array of edge identifiers, each corresponds to an edge going out of the node.

   DAG = {
     "adjacency": {
       "a": ["1", "2"],
       "b": ["3"]
     },
     "nodes": {
       "a": {
         // data
       },
       "b": {
         // data
       },
       "c": {
         // data
       }
     },
     "edges": {
       "1": {
         "from": "a", "to": "b",
         "data": {
           // data
         }
       },
       "2": {
         "from": "a", "to": "b",
         "data": {
           // data
         }
       },
       "3": {
         "from": "b", "to": "c",
         "data": {
           // data
         }
       }
     }
   }