I guess this is the downside of making it generic - it might be difficult to decide what should be the default. And once the default has been coded in the JSON Schema and AS7 XSD, then won't all connector configurations that want to support writes have to use `readonly="false"`?

The other option is to have the default for `readonly` be `false` like you have it here. Perhaps that is best, even though it's not "safest".