Hi Guys I'm trying to create a question in a form where one is asked for an ID however I want the ID entred checked in the background against a predefined list and if it exist the data collector can move to next question and if the ID in not in the list they get a prompt for required_message to enter correct ID. I need toknow what constraint in my X-Form to make this work.
If the ID should match a particular format, then you can use a regular expression. https://docs.opendatakit.org/form-regex has more.
If you really want to match an ID from a list, you can try using pulldata() to match against an ID in a CSV. http://xlsform.org/en/#pre-loading-csv-data has more.