[
    {
        "uid": { "type": "User", "id": "alice"} ,
        "attrs": {
            "age": 18
        },
        "parents": [{"type": "UserGroup", "id": "jane_friends"}]
    },
    {
        "uid": { "type": "UserGroup", "id": "jane_friends" },
        "attrs": {},
        "parents": []
    },
    {
        "uid": { "type": "Action", "id": "view"},
        "attrs": {},
        "parents": []
    },
    {
        "uid": { "type": "Photo", "id": "VacationPhoto94.jpg"},
        "attrs": {},
        "parents": [{ "type": "Album", "id": "jane_vacation" }]
    },
    {
        "uid": { "type": "Album", "id": "jane_vacation" },
        "attrs": {},
        "parents": []
    }
]