What is the purpose of the data and the items attribute in response body?

Question

In some API calls like listwallettransactions and listassettransactions, the response​ body always contains two fields DATA and ITEMS.

I checked the developer guide but have no clues what are the purposes of these two fields? It seems they are always empty even if I fill in some json data when calling send API like below:

{
    "method": "send",
    "params": [
        "1Rfo11oxnpxMS6YeqWm9h8ZqC4ygHEKKYir1Qy",
        {
            "assetX": 100,
            "data": {
                "json": {
                    "payer": "PayerCompanyUUID",
                    "receiver": "ReceiverCompanyUUID"
                }
            }
        }
    ]
}

Answer 1

The "data" field is for transaction metadata embedded in a separate output (using an API like sendwithdata) and the "items" field is for stream items published in that wallet transaction. Inline metadata is not currently displayed in the output from these APIs.