Daniel ben Yehudah Dayyan was a Jewish liturgical poet, who lived at Rome in the middle of the fourteenth century CE. He was the grandfather of Daniel ben Samuel ha-Rofe, rabbi at Tivoli. According to Samuel David Luzzatto, Daniel ben Yehudah was the author of the well-known piyyut "Yigdal" containing a doxology based upon the thirteen articles of belief of Maimonides. This piyyut, which forms part of the morning prayer among the Ashkenazim, and is sung by the Sephardim on the eve of Sabbaths and holy days, is included in the Romaniote ritual for Saturday evening. (adapted from wikipedia)