compareAnswersets: Boolean!

Whether an answer set already holds the values given, so that a caller about to write them can tell whether writing would change anything. Only the answers named are compared. A set holding more than it was asked about still matches, and a value naming an element the form does not ask is ignored rather than counted as a difference. Answered here rather than by the forms service because the answer set may be held by either engine, and only this application knows which. An answer set it holds no submission for is one it knows nothing about, which is not a match — so the caller writes, and the write applies its own rules.