Professor of Syriac at the Collegium Sapientiae, and then of liturgy at the Pontifical Academy, Rome; nephew of J. S. Assemani , and cousin of S. E. Assemani . His projected Codex Liturgicus Ecclesiae Universae was to cover all rites in 15 volumes, but only 5 appeared (1749–1766; repr. 1968); this remains a valuable resource. Among his other works are Latin translations of Collection of Canons by ʿAbdishoʿ and of the Nomocanon of Bar ʿEbroyo (both published by A. Mai, in his Scriptorum veterum nova collectio 10; 1838).