# sputnik - Deployment Meta Language

Given DeviceTypes, DeviceBlueprints and SystemBlueprints have no knowledge of the underlying devices and can refer to multiple different AWS resources, Sputnik has a "meta-language" in order to map these resources updon deployment.

## Account related metadata

The deployment service supports the following tags that are pre-populated at first sputnik deployment in your account:

* AWS_ACCOUNT
* AWS_REGION
* THING_NAME
* CORE
* CORE_ARN
* CORE_CERTIFICATE_ARN
* DATA_BUCKET
* DATA_BUCKET_S3_URL
* IOT_ENDPOINT

These account related metadata are used in the specs by encapsulating them in brackets [ ].

```
Example: ml-demo-squeezenet-v1.0
{
    "FunctionDefinitionVersion": {
        "Functions": [{
            "FunctionArn": "arn:aws:lambda:[AWS_REGION]:[AWS_ACCOUNT]:function:sputnik-gg-ml-inference-squeezenet-demo-python:Prod",
            "FunctionConfiguration": {
            		...
            
```

## Business logic metadata

### DeviceTypeMappings

In the DeviceBlueprints, some fields require to map to a specific DeviceType. For this the deviceTypeMappings object is used.

```
Example: ml-demo-squeezenet-v1.0
{
    "FunctionDefinitionVersion": {
        "Functions": [{
            "FunctionArn": "arn:aws:lambda:[AWS_REGION]:[AWS_ACCOUNT]:function:sputnik-gg-ml-inference-squeezenet-demo-python:Prod",
            "FunctionConfiguration": {
                ...
            }
        }]
    }...
}
```
In this sample. **CAM\_STREAM\_ID\_1** will be replaced by **picamera-vcsm** for the **rpi3-sense-hat-picamera-v1.0** DeviceType.

### !GetAtt
This metadata tag in the specs allows to pull data from inferred data from a SystemBlueprint.

A system can consist of 2 devices.
In a SystemBlueprint these 2 devices are referenced by the **ref** tag.

By using the !GetAtt, upon deployment, we can reference information from the very specific device that is referenced by the system form the blueprint.

```
Example: sample-system-v1.0
{
    "Devices": [{
            ...
            "ref": "DEVICE",
            "spec": {
                "FunctionDefinitionVersion": {
                    "Functions": [{
                        ...
                    }, {
                        "FunctionArn": "arn:aws:lambda:[AWS_REGION]:[AWS_ACCOUNT]:function:sputnik-simple-greengrass-device-demo-python:Prod",
                        "FunctionConfiguration": {
                            "EncodingType": "json",
                            "Environment": {
                                "Variables": {
                                    ...
                                    "GATEWAY": "!GetAtt[GATEWAY.thingName]",
                                    ...
                   ...
          }, {
            ...
            "ref": "GATEWAY",
            "spec": {
            		...
            }
          }
    }
}
```