# Using JSONPath paths
Using JSONPath paths

**Managing state and transforming data**  
Learn about [Passing data between states with variables](workflow-variables.md) and [Transforming data with JSONata](transforming-data.md).

In the Amazon States Language, a *path* is a string beginning with `$` that you can use to identify components within JSON text. Paths follow [JsonPath](https://datatracker.ietf.org/wg/jsonpath/about/) syntax, which is only available when the `QueryLanguage` is set to JSONPath. You can specify a path to access subsets of the input when specifying values for `InputPath`, `ResultPath`, and `OutputPath`.

You must use square bracket notation if your field name contains any character that is not included in the `member-name-shorthand` definition of the [JsonPath ABNF](https://www.ietf.org/archive/id/draft-ietf-jsonpath-base-21.html#jsonpath-abnf) rule. Therefore, to encode special characters, such as punctuation marks (excluding `_`), you must use square bracket notation. For example, `$.abc.['def ghi']`. 

## Reference Paths


A *reference path* is a path whose syntax is limited in such a way that it can identify only a single node in a JSON structure:
+ You can access object fields using only dot (`.`) and square bracket (`[ ]`) notation.
+ Functions such as `length()` aren't supported.
+ Lexical operators, which are non-symbolic, such as `subsetof` aren't supported.
+ Filtering by regular expression or by referencing another value in the JSON structure is not supported.
+ The operators `@`, `,`, `:`, and `?` are not supported

For example, if state input data contains the following values:

```
{
  "foo": 123,
  "bar": ["a", "b", "c"],
  "car": {
      "cdr": true
  }
}
```

The following reference paths would return the following.

```
$.foo => 123
$.bar => ["a", "b", "c"]
$.car.cdr => true
```

Certain states use paths and reference paths to control the flow of a state machine or configure a state's settings or options. For more information, see [Modeling workflow input and output path processing with data flow simulator](https://aws.amazon.com/blogs/compute/modeling-workflow-input-output-path-processing-with-data-flow-simulator/) and [Using JSONPath effectively in AWS Step Functions](https://aws.amazon.com/blogs/compute/using-jsonpath-effectively-in-aws-step-functions/).

### Flattening an array of arrays


If the [Parallel workflow state](state-parallel.md) or [Map workflow state](state-map.md) state in your state machines return an array of arrays, you can transform them into a flat array with the [ResultSelector](input-output-inputpath-params.md#input-output-resultselector) field. You can include this field inside the Parallel or Map state definition to manipulate the result of these states.

To flatten arrays, use the syntax: `[*]` in the `ResultSelector` field as shown in the following example.

```
"ResultSelector": {
    "flattenArray.$": "$[*][*]"
  }
```

For examples that show how to flatten an array, see *Step 3* in the following tutorials:
+ [Processing batch data with a Lambda function in Step Functions](tutorial-itembatcher-param-task.md)
+ [Processing individual items with a Lambda function in Step Functions](tutorial-itembatcher-single-item-process.md)