# Specifying blueprint parameters
<a name="developing-blueprints-code-parameters"></a>

The configuration file contains blueprint parameter specifications in a `parameterSpec` JSON object. `parameterSpec` contains one or more parameter objects.

```
"parameterSpec": {
    "<parameter_name>": {
      "type": "<parameter-type>",
      "collection": true|false, 
      "description": "<parameter-description>",
      "defaultValue": "<default value for the parameter if value not specified>"
      "allowedValues": "<list of allowed values>" 
    },
    "<parameter_name>": {    
       ...
    }
  }
```

The following are the rules for coding each parameter object:
+ The parameter name and `type` are mandatory. All other properties are optional.
+ If you specify the `defaultValue` property, the parameter is optional. Otherwise the parameter is mandatory and the data analyst who is creating a workflow from the blueprint must provide a value for it.
+ If you set the `collection` property to `true`, the parameter can take a collection of values. Collections can be of any data type.
+ If you specify `allowedValues`, the AWS Glue console displays a dropdown list of values for the data analyst to choose from when creating a workflow from the blueprint.

The following are the permitted values for `type`:


| Parameter data type | Notes | 
| --- | --- | 
| String | - | 
| Integer | - | 
| Double | - | 
| Boolean | Possible values are true and false. Generates a check box on the Create a workflow from <blueprint> page on the AWS Glue console. | 
| S3Uri | Complete Amazon S3 path, beginning with s3://. Generates a text field and Browse button on the Create a workflow from <blueprint> page. | 
| S3Bucket | Amazon S3 bucket name only. Generates a bucket picker on the Create a workflow from <blueprint> page. | 
| IAMRoleArn | Amazon Resource Name (ARN) of an AWS Identity and Access Management (IAM) role. Generates a role picker on the Create a workflow from <blueprint> page. | 
| IAMRoleName | Name of an IAM role. Generates a role picker on the Create a workflow from <blueprint> page. |