Note that ISO 15924 includes some codes for script variants (for example, "Hans" and "Hant" for simplified and traditional forms of Chinese characters) that are unified within Unicode and ISO/IEC 10646. These script variants are most often encoded for bibliographic purposes, but are not always significant from a linguistic point of view (for example, "Latf" and "Latg" script codes for the Fraktur and Gaelic variants of the Latin script, which are mostly encoded with regular Latin letters in Unicode and ISO/IEC 10646). They may occasionally be useful in language tags to expose orthographic or semantic differences, with different analysis of letters, diacritics, and digraphs/trigraphs as default grapheme clusters, or differences in letter casing rules.