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jsonfreebasemql

Inverting MQL queries

Chapter 3 of the MQL reference (specifically section 3.2.6) talks about inverting queries to obtain the same data in a different structure, either to simplify the query or massage the data to return a structure that's similar to your own.

So I start with the following query:

https://api.freebase.com/api/service/mqlread?query={"query":{"type":"/automotive/model","name":"Ford Taurus","generations":[]}}

Readable version:

{
    "type":"/automotive/model",
    "name":"Ford Taurus",
    "generations":[]
}

Results:

{
  "code": "/api/status/ok",
  "result": {
    "generations": [
      "First Generation Ford Taurus",
      "Second Generation Ford Taurus",
      "Fifth Generation Ford Taurus",
      "Sixth Generation Ford Taurus",
      "Fourth Generation Ford Taurus",
      "Third Generation Ford Taurus"
    ],
    "name": "Ford Taurus",
    "type": "/automotive/model"
  },
  "status": "200 OK",
  "transaction_id": "cache;cache04.p01.sjc1:8101;2013-04-25T22:05:58Z;0012"
}

But I want to make the query generation-centric, so I modify it like so:

https://api.freebase.com/api/service/mqlread?query={"query":[{"type":"/automotive/generation","model":"Ford Taurus","name":null}]}

Readable version:

[{
    "type":"/automotive/generation",
    "model":"Ford Taurus",
    "name":null
}]

Results:

{
  "code": "/api/status/ok",
  "result": [
    {
      "model": "Ford Taurus",
      "name": "First Generation Ford Taurus",
      "type": "/automotive/generation"
    },
    {
      "model": "Ford Taurus",
      "name": "Third Generation Ford Taurus",
      "type": "/automotive/generation"
    }
  ],
  "status": "200 OK",
  "transaction_id": "cache;cache01.p01.sjc1:8101;2013-04-25T23:00:35Z;0010"
}

My inverted query only returns two generations! Please help me figure out why this is.

Solution

  • If you look at the Freebase schema page for Automobile Generation you'll see that the model property has been deprecated and replaced by a models property. Making that change to your query:

    [{
  "type": "/automotive/generation",
  "models": "Ford Taurus",
  "name": null
}]

    Gives you the expected result set:

    [
  {
    "models": "Ford Taurus",
    "name": "First Generation Ford Taurus",
    "type": "/automotive/generation"
  },
  {
    "models": "Ford Taurus",
    "name": "Second Generation Ford Taurus",
    "type": "/automotive/generation"
  },
  {
    "models": "Ford Taurus",
    "name": "Fifth Generation Ford Taurus",
    "type": "/automotive/generation"
  },
  {
    "models": "Ford Taurus",
    "name": "Sixth Generation Ford Taurus",
    "type": "/automotive/generation"
  },
  {
    "models": "Ford Taurus",
    "name": "Fourth Generation Ford Taurus",
    "type": "/automotive/generation"
  },
  {
    "models": "Ford Taurus",
    "name": "Third Generation Ford Taurus",
    "type": "/automotive/generation"
  }
]