The JointJS graph JSON representation has the following format:

    {
        cells: [// Array of cells (ie. links and elements).
            {
                id: '3d90f661-fe5f-45dc-a938-bca137691eeb',// Some randomly generated UUID.
                type: 'basic.Rect',
                attrs: {
                    'stroke': '#000'
                },
                position: {
                    x: 0,
                    y: 50
                },
                angle: 90,
                size: {
                    width: 100,
                    height: 50
                },
                z: 2,
                embeds: [
                    '0c6bf4f1-d5db-4058-9e85-f2d6c74a7a30',
                    'cdbfe073-b160-4e8f-a9a0-22853f29cc06'
                ],
                parent: '31f348fe-f5c6-4438-964e-9fc9273c02cb'
                // ... and some other, maybe custom, data properties
            }
        ]
    }