Ioannes 517 was a deacon; he was made bishop of Olivolo by the people when the see was apparently abandoned by Christophoros 57 ("Olyvolensis namque sedis ... Iohanni diacono electo a plebe fuerat adtributa"); after the return from Francia of Christophoros 57 with Phortounatos 2, Phortounatos 2 tried to restore Christophoros 57 to the see and he had Ioannes 517 arrested and detained; Ioannes 517 however escaped and fled to the dux of Venetia, Obelerios 1; later Christophoros 57 regained his see and Ioannes 517 returned home ("ad propriam domum") a deacon: John the Deacon, Cron. Ven., pp. 102-103. In 806, after Phortounatos 2 fled to Francia, Ioannes 517, deacon and former bishop of Olivolo, was made patriarch of Grado in his place: John the Deacon, Cron. Ven., p. 103 ("Iohannes vero diaconus, qui electus fuerat in episcopatu Olyvolensi, ordinatus est patriarcha"). After four years as patriarch of Grado he was deposed by a synod and replaced by Phortounatos 2; he had adorned with marble columns and plaques the shrines of Hermagoras and Fortunatus and of Hyllaris and Tacianus, as well as the chapel of St Mark, and he donated a ciborium to hang over the altar of the Church of Sancta Maria: John the Deacon, Cron. Ven., p. 105.

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