rules:
  starts-with-a:
    given: $.*
    then:
      function: pattern
      functionOptions:
        match: "^a"
  absent:
    given: $
    then:
      field: missing
      function: pattern
      functionOptions:
        match: "^a"
  one-of:
    given: $.s
    then:
      function: xor
      functionOptions:
        properties: [p, q]