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# Sparnatural Query JSON format


## How it works : onQueryUpdated / loadQuery

Sparnatural emits the [`queryUpdated` event](http://docs.sparnatural.eu/Javascript-integration.html#queryupdated-event) each time the query is modified. This event contains 3 files : the generated SPARQL query string, the SPARQL query in JSON in the sparqljs syntax, and a custom JSON data structure that encodes the query. This custom JSON data structure is specific to Sparnatural, and enables it to **load previously generated query**, using the method [**`sparnatural.loadQuery(jsonQuery)`**](http://docs.sparnatural.eu/Javascript-integration.html#sparnatural-element-api).

This allows to implement 2 important features to showcase your knowledge graph :

1. The ability to prepare **sample queries that can be loaded** in a single click to initialize Sparnatural with your query
2. The ability to **encode the query in a URL parameter** and load directly Sparnatural with the query received. This enable the users to share direct links to their preferred queries, and your knowledge graph goes viral ;-)

This is illustrated in the following code snippet :


```javascript
$( document ).ready(function($) {          

        const sparnatural = document.querySelector("spar-natural");
        
        sparnatural.addEventListener("queryUpdated", (event) => {
                // here we get the SPARQL query string and the JSON data structure
                // if integrating with YasQE we set the value :
                queryString = sparnatural.expandSparql(event.detail.queryString);
                yasqe.setValue(queryString);

                // and we could save the JSON query for later, e.g. to pass it as a parameter in a URL
                document.getElementById('query-json').value = JSON.stringify(event.detail.queryJson);
        });


        // if we have received a JSON data structure as a URL parameter "?query="
        // then uncompress it, and pass it to the loadQuery() function of Sparnatural
      var UrlString = window.location.search;
      var urlParams = new URLSearchParams(UrlString);
      if (urlParams.has("query") === true) {
        var compressedJson = urlParams.get("query") ;
        var compressCodec = JsonUrl('lzma');
        compressCodec.decompress(compressedJson).then(json => {
          sparnatural.loadQuery(JSON.parse(json)) ;
        });
      }
});


// if we have a dropdown to select example query from...
document.getElementById('select-examples').onchange = function() {
        var key = $('#select-examples option:selected').val();
        sparnatural.loadQuery(sampleQueries[key]) ;
}

```

## JSON query example

The following query in Sparnatural (_All Artworks displayed in French or Italian museums, and created in the 19th century, with their creation date_) :

![Sparnatural query example](/assets/images/screenshot-JSON-data-structure.png)

Is modelled in the following JSON data structure :

```json
{
  "distinct": true,
  "variables": [
    {
      "termType": "Variable",
      "value": "Artwork_1"
    },
    {
      "termType": "Variable",
      "value": "Date_6"
    }
  ],
  "order": null,
  "branches": [
    {
      "line": {
        "s": "Artwork_1",
        "p": "http://ontologies.sparna.fr/sparnatural-demo-dbpedia#displayedAt",
        "o": "Museum_2",
        "sType": "http://ontologies.sparna.fr/sparnatural-demo-dbpedia#Artwork",
        "oType": "http://ontologies.sparna.fr/sparnatural-demo-dbpedia#Museum",
        "values": []
      },
      "children": [
        {
          "line": {
            "s": "Museum_2",
            "p": "http://ontologies.sparna.fr/sparnatural-demo-dbpedia#country",
            "o": "Country_4",
            "sType": "http://ontologies.sparna.fr/sparnatural-demo-dbpedia#Museum",
            "oType": "http://ontologies.sparna.fr/sparnatural-demo-dbpedia#Country",
            "values": [
              {
                "label": "France (3987)",
                "rdfTerm": {
                  "type": "uri",
                  "value": "http://fr.dbpedia.org/resource/France"
                }
              },
              {
                "label": "Italy (1091)",
                "rdfTerm": {
                  "type": "uri",
                  "value": "http://fr.dbpedia.org/resource/Italie"
                }
              }
            ]
          },
          "children": []
        }
      ]
    },
    {
      "line": {
        "s": "Artwork_1",
        "p": "http://ontologies.sparna.fr/sparnatural-demo-dbpedia#creationYear",
        "o": "Date_6",
        "sType": "http://ontologies.sparna.fr/sparnatural-demo-dbpedia#Artwork",
        "oType": "http://ontologies.sparna.fr/sparnatural-demo-dbpedia#Date",
        "values": [
          {
            "label": "from 1800 to 1901",
            "start": "1799-12-31T23:50:40.000Z",
            "stop": "1901-12-31T23:50:38.000Z"
          }
        ]
      },
      "children": []
    }
  ]
}
```

## JSON data structure reference

Basically, the JSON data structure encodes a bit more information than the generated SPARQL query, to make our life easier when parsing the data structure to initialize Sparnatural with it. It adds:
  - The labels of the values
  - The types of all subjects and objects
  - The tree-like structure that Sparnatural uses, which would be hard to guess by looking at the SPARQL string

The data structure is composed of a top "Query" structure, that contains "branches". Each "branch" contains on "query line", corresponding to one line of the Sparnatural interface, and the "children" of this line, that are the lines under it in the Sparnatural interface.

### Query structure

```json
{
  "distinct": true,
  "variables": [
   {
      "termType": "Variable",
      "value": "this"
    },
    {
      "termType": "Variable",
      "value": "that"
    }
  ],
  "order": null,
  "branches": [
    ...
  ]
}
```

- `distinct` : whether the `DISTINCT` SPARQL keyword should be added
- `variables` : ordered list of variables selected in the `WHERE` clause. `termType` is always `Variable`, and `value` is the variable name (without "?")
- `order` : e.g. `"asc"` or `"desc"` depending on sort direction. Or `null` if no sort. The sort is always on the first column.
- `branches` : ordered list of query branches, each containing a "tree" of criteria under it

### Query branch structure

```json
{
      "line": {
        ...
      },
      "children": [
        ...
      ],
      "optional": true,
      "notExists": false,
    },
```

- `line` : one single query line / criteria
- `children` : the children of that line / criteria, the ones that are below it in the Sparnatural query builder
- `optional` : whether the line and all its children are optional (use a SPARQL "OPTIONAL")
- `notExists` : whether the line and all its children are negative (use a SPARQL "FILTER NOT EXISTS")

### Query line structure

```json
{
  "line": {
    "s": "Museum_2",
    "p": "http://ontologies.sparna.fr/sparnatural-demo-dbpedia#country",
    "o": "Country_4",
    "sType": "http://ontologies.sparna.fr/sparnatural-demo-dbpedia#Museum",
    "oType": "http://ontologies.sparna.fr/sparnatural-demo-dbpedia#Country",
    "values": [
      {
        "label": "France (3987)",
        "rdfTerm": {
          "type": "uri",
          "value": "http://fr.dbpedia.org/resource/France"
        }
      },
      {
        "label": "Italy (1091)",
        "rdfTerm": {
          "type": "uri",
          "value": "http://fr.dbpedia.org/resource/Italie"
        }
      }
    ]
  },
  "children": []
}
```

- `s` : variable of the subject
- `p` : URI of the predicate
- `o` : variable of the object
- `sType` : URI of the selected type of the subject
- `oType` : URI of the selected type of the object
- `values` : arrays of values selected for the object, if any

### Values

The structure of the values depend on the structure of the criteria/line. This can be :

- A URI selection widget (dropdown list, autocomplete, tree widget):

If the value is a URI:

```json
  {
        "label": "Italy (1091)",
        "rdfTerm": {
          "type": "uri",
          "value": "http://fr.dbpedia.org/resource/Italie"
        }
  }
```


If the value is a Literal (with a language):

```json
  {
        "label": "foo",
        "rdfTerm": {
          "type": "literal",
          "value": "foo",
          "xml:lang": "en"
        }
  }
```

If the value is a Literal (with a datatype):

```json
  {
        "label": "1",
        "rdfTerm": {
          "type": "literal",
          "value": "1",
          "datatype": "http://www.w3.org/2001/XMLSchema#integer"
        }
  }
```

- A time/date selection widget:

```json
  {
    "label": "From 1800 to 1901",
    "start": "1800-01-01T00:00:00",
    "stop": "1901-12-31T23:59:59"
  }
```

- A boolean widget:

```json
  {
    "label": "Vrai",
    "boolean": true
  }
```

- A regex search widget:

```json
  {
    "label": "...",
    "search": "..."
  }
```

- A number widget:

```json
  {
    "label": "between 10000 and 100000",
    "min": 10000,
    "max": 100000
  }
```

### Aggregated variables

If the query has aggregated variables (such as `COUNT(?x)`), the variable query structure changes to the following:

```json
{
  "distinct": true,
  "variables": [
    {
      "expression": {
        "type": "aggregate",
        "aggregation": "count",
        "distinct": false,
        "expression": {
          "termType": "Variable",
          "value": "Artwork_1"
        }
      },
      "variable": {
        "termType": "Variable",
        "value": "Artwork_1_count"
      }
    }
  ],
}
```