Common patterns: 把/将 A 定为 B (designate A as B), A 被定为 B (A is designated as B). The 为 here is read wéi (second tone), not wèi.
register
定为 is formal and official, commonly seen in laws, regulations, and official announcements. In casual speech, people say 定成 (dìngchéng) or 算作 (suànzuò) instead.