This is one part of the Verona Online Assessment Standards. All messages are sent via the postMessage function of the html page. The schemer takes the page root of its parent as target (parent.window), and the application binds the function call to the iframe element of the schemer. Most important, the message body carries as first parameter the operationId of the message. The html page MUST contain a script-tag with metadata. The syntax and structure of this data are described here.
Ready Notification
The schemer announces that it's code is loaded and initialized so the communication can start.
Accepts the following message:
{
"metadata": "string"
}
Start Command
The application sends parameters for editing the coding scheme and commands the start of user interaction.
Accepts the following message:
{
"sessionId": "idk8ur5jf9ru5jk",
"codingScheme": "<CodingScheme> <Variable id=\"text-field_2\" label=\"text-field_2\"> <RuleBased> <Transform>DATE_TO_ISO</Transform> </RuleBased> <Code code=\"1\" score=\"11\" label=\"111\"> <Rule method=\"MATCH\"> <Parameter>2021-12-04</Parameter> </Rule> </Code> <Code code=\"2\" score=\"22\" label=\"222\"> <Rule method=\"MATCH\"> <Parameter>2022-12-04</Parameter> </Rule> </Code> </Variable> </CodingScheme>",
"codingSchemeType": "iqb@1.0",
"variables": [
{
"id": "^0$",
"type": "string",
"format": "text-selection",
"multiple": false,
"nullable": false,
"values": [
{
"value": "string",
"label": "string"
}
],
"valuePositionLabels": [
"string"
],
"valuesComplete": false,
"page": "string"
}
],
"schemerConfig": {
"directDownloadUrl": "https://www.iqb-supercoder.de/download/iskeid-34e845-didmmemdkek"
}
}
Scheme Changed Notification
The coding scheme of the unit has changed.
Accepts the following message:
{
"sessionId": "idk8ur5jf9ru5jk",
"timeStamp": "2019-08-24T14:15:22Z",
"codingScheme": "string",
"codingSchemeType": "iqb@1.0",
"dependenciesToCode": [
{
"id": "https://short-answer-supercoder.iqb-berlin.de",
"type": "file"
}
]
}
The session id flags all communication. If a message has no or empty session id, it's not processed. The session id is unique and was generated by the application. Any simple algorithm would work. The session id helps to link the correct unit with the data of the message. Using the id of the editor hosting html element is less reliable, because the element could be reused with another unit.