Not ambiguous really. You know it's <first> (<second/middle>) (<third (rare)>)? (<dad's surname>) (<mom's surname>) and names are typically a single WORD, but may (rarely) have a prefix like De/Della (except for the first name).

---

Well, this guys mentions they treat "Roberto Antonio" as a single name, and not as a first and second/middle name. I don't see it that way (Spanish, Chile). Here there's a lot of way too common first names (María, José), so most go by both or just he second one, but legally they just have a common first name (and thus, many systems use both names to avoid confusion over mail and email).