Source

{
    "type": "object",
    "properties": {
        "site_id": {
            "type": "string",
            "const": "ursy.art"
        },
        "url": {
            "type": "string",
            "maxLength": 2048,
            "format": "uri"
        },
        "source_revision": {
            "type": "string",
            "maxLength": 300
        },
        "observed_at": {
            "type": "string",
            "maxLength": 40,
            "format": "date-time"
        }
    },
    "required": [
        "site_id",
        "url",
        "source_revision",
        "observed_at"
    ],
    "additionalProperties": false
}