:params
  "data": {
    "System": [
      {
        "name": "System 1",
        "datasets": [
          {
            "name": "Customers"
          }
        ]
      },
      {
        "name": "System 2",
        "datasets": [
          {
            "name": "Customers"
          }
        ]
      },
      {
        "name": "System 3",
        "datasets": [
          {
            "name": "Products"
          }
        ]
      }
    ]
  }

UNWIND {data} as data
UNWIND data.System as systems
UNWIND systems.datasets as datasets
MERGE (sy:System { name: systems.name})
    ON CREATE SET sy.status='New'
    ON MATCH SET  sy.status='Updated'
MERGE (da:Dataset { name: datasets.name})
MERGE (sy)-[:CONTAINS_DATASET]->(dan:Dataset { name: datasets.name })
return *