Primitive type 'int'
Integer numbers (-1,0,1,2, 100, 3398129, etc.) are precise numbers that are results of counting and enumerating. Integer numbers are discrete, the set of integers is infinite but countable. No arbitrary limit is imposed on the range of integer numbers. Two NULL flavors are defined for the positive and negative infinity.
32 bit number; for values larger than this, use decimal
All FHIR elements must have a @value or children
hasValue() or (children().count() > id.count())
unique id for the element within a resource (for internal references)
Must have either extensions or value[x], not both