External attributes
ExternalAttributes
are a data type that can be used to communicate data between parties that is not inherently part of OTM. This allows you to extend the data present in OTM without the need to change the specification. This usually will be administrative, or company-specific data. Note though, that if something can be modeled using just OTM entities it should be done that way. External attributes are often used to provide IDs that are not UUIDs but still need to be communicated.
External attributes are nothing more than a list of key-values. This is an example of what it could look like:
{
"customerId": "1234",
"shift": "Morning shift"
}