As part of a project to convert the Taishō Tripiṭaka—the scholarly standard edition of the Chinese Buddhist canon—into TEI-compliant XML, we are migrating Siddhaṃ script data from an internal transcription rule to Unicode to facilitate better data exchange. Siddhaṃ is a medieval Brahmic script spread to East Asia approximately between the 6th and the 8th centuries as a medium for Buddhist texts; it has been preserved there as a liturgical alphabet for transcribing Indic syllables.

Beyond its complex ligature system inherent to Indic abugidas, Siddhaṃ has acquired ideographic or iconic qualities in East Asia. Due to its religious role and the influence of the logographic Chinese writing system, specific variants have become associated with fixed meanings. In the Japanese Esoteric Buddhist (Mikkyō) tradition, this differentiation of variants is particularly systematic in the use of shuji (種字; “seed syllables”) to represent specific deities.

During the migration process, we compared our original notations in the Taishō Tripiṭaka against facsimile images and other Siddhaṃ resources. This examination revealed various non-standard glyphs, including irregular akṣaras (syllables), idiosyncratic variants, and possibly unencoded symbols and conjuncts. This presentation provides a preliminary overview of Siddhaṃ usage in the Taishō Tripiṭaka, evaluates current Unicode and font support, and discusses optimal encoding strategies for academic Siddhaṃ texts.