{ "type": "object", "title": "State Event", "description": "In addition to the Room Event fields, State Events have the following additional fields.", "allOf":[{ "$ref": "core-event-schema/room_event.json" }], "properties": { "state_key": { "type": "string", "description": "A unique key which defines the overwriting semantics for this piece of room state. This value is often a zero-length string. The presence of this key makes this event a State Event." }, "prev_content": { "type": "object", "description": "Optional. The previous ``content`` for this event. If there is no previous content, this key will be missing." } }, "required": ["state_key"] }