# Creating a Neptune GraphMappingConfig
<a name="dms-neptune-graph-mapping"></a>

The `GraphMappingConfig` that you create specifies how data extracted from a source data store should be loaded into a Neptune DB cluster. Its format differs depending on whether it is intended for loading RDF data or for loading property-graph data.

For RDF data, you can use the W3 [R2RML](https://www.w3.org/TR/r2rml/) language for mapping relational data to RDF.

If you are loading property-graph data to be queried using Gremlin, you create a JSON object for `GraphMappingConfig`.

## GraphMappingConfig Layout for RDF/SPARQL Data
<a name="dms-neptune-graph-mapping-sparql"></a>

If you are loading RDF data to be queried using SPARQL, you write the `GraphMappingConfig` in [R2RML](https://www.w3.org/TR/r2rml/). `R2RML` is a standard W3 language for mapping relational data to RDF. Here is one example:

```
@prefix rr: <http://www.w3.org/ns/r2rml#> .
@prefix ex: <http://example.com/ns#> .

<#TriplesMap1>
    rr:logicalTable [ rr:tableName "nodes" ];
    rr:subjectMap [
        rr:template "http://data.example.com/employee/{id}";
        rr:class ex:Employee;
    ];
    rr:predicateObjectMap [
        rr:predicate ex:name;
        rr:objectMap [ rr:column "label" ];
    ] .
```

Here is another example:

```
@prefix rr: <http://www.w3.org/ns/r2rml#> .
@prefix ex: <http://example.com/#> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .

<#TriplesMap2>
    rr:logicalTable [ rr:tableName "Student" ];
    rr:subjectMap   [ rr:template "http://example.com/{ID}{Name}";
                      rr:class foaf:Person ];
    rr:predicateObjectMap [
        rr:predicate ex:id ;
        rr:objectMap  [ rr:column "ID";
                        rr:datatype xsd:integer ]
    ];
    rr:predicateObjectMap [
        rr:predicate foaf:name ;
        rr:objectMap  [ rr:column "Name" ]
    ] .
```

The W3 Recommendation at [R2RML: RDB to RDF Mapping Language](https://www.w3.org/TR/r2rml/) provides details of the language.

## GraphMappingConfig Layout for Property-Graph/Gremlin Data
<a name="dms-neptune-graph-mapping-gremlin"></a>

A comparable `GraphMappingConfig` for property-graph data is a JSON object that provides a mapping rule for each graph entity to be genereated from the source data. The following template shows what each rule in this object looks like:

```
{
  "rules": [
    {
      "rule_id": "(an identifier for this rule)",
      "rule_name": "(a name for this rule)",
      "table_name": "(the name of the table or view being loaded)",
      "vertex_definitions": [
        {
          "vertex_id_template": "{col1}",
          "vertex_label": "(the vertex to create)",
          "vertex_definition_id": "(an identifier for this vertex)",
          "vertex_properties": [
            {
              "property_name": "(name of the property)",
              "property_value_template": "{col2} or text",
              "property_value_type": "(data type of the property)"
            }
          ]
        }
      ]
    },
    {
      "rule_id": "(an identifier for this rule)",
      "rule_name": "(a name for this rule)",
      "table_name": "(the name of the table or view being loaded)",
      "edge_definitions": [
        {
          "from_vertex": {
            "vertex_id_template": "{col1}",
            "vertex_definition_id": "(an identifier for the vertex referenced above)"
          },
          "to_vertex": {
            "vertex_id_template": "{col3}",
            "vertex_definition_id": "(an identifier for the vertex referenced above)"
          },
          "edge_id_template": {
            "label": "(the edge label to add)",
            "template": "{col1}_{col3}"
          },
          "edge_properties":[
            {
              "property_name": "(the property to add)",
              "property_value_template": "{col4} or text",
              "property_value_type": "(data type like String, int, double)"
            }
          ]
        }
      ]
    }
  ]
}
```

Note that the presence of a vertex label implies that the vertex is being created here, whereas its absence implies that the vertex is created by a different source, and this definition is only adding vertex properties.

Here is a sample rule for an employee record:

```
{
  "rules": [
    {
      "rule_id": "1",
      "rule_name": "vertex_mapping_rule_from_nodes",
      "table_name": "nodes",
      "vertex_definitions": [
        {
          "vertex_id_template": "{emp_id}",
          "vertex_label": "employee",
          "vertex_definition_id": "1",
          "vertex_properties": [
            {
              "property_name": "name",
              "property_value_template": "{emp_name}",
              "property_value_type": "String"
            }
          ]
        }
      ]
    },
    {
      "rule_id": "2",
      "rule_name": "edge_mapping_rule_from_emp",
      "table_name": "nodes",
      "edge_definitions": [
        {
          "from_vertex": {
            "vertex_id_template": "{emp_id}",
            "vertex_definition_id": "1"
          },
          "to_vertex": {
            "vertex_id_template": "{mgr_id}",
            "vertex_definition_id": "1"
          },
          "edge_id_template": {
            "label": "reportsTo",
            "template": "{emp_id}_{mgr_id}"
          },
          "edge_properties":[
            {
              "property_name": "team",
              "property_value_template": "{team}",
              "property_value_type": "String"
            }
          ]
        }
      ]
    }
  ]
}
```