XPath rules declare new properties using the type attribute, which can be eg Boolean or Integer. The corresponding multivalued properties are declared with a type attribute like List<Boolean> or List<Integer>, since the properties refactoring of this summer.

I just realised that < and > are forbidden characters in xml attributes, so those properties cannot be used lol

I think I'll fix that with a List[Integer] and List[Boolean] syntax, à la Scala