GIOVANNI V bar Abgré. - Nestorian Catholicos (900-905), the first to commit himself in writing after his election to perform his duties well and who ordered all his successors to do the same.
Of him are preserved the *Canons* for the service of the altar and the *Responses* to ecclesiastical questions, works that contain liturgical casuistry.
With G. d'A. the so-called classical period of canon law comes to a close. He can also be considered the synthesizer of canonical juridical thought, a precise precedent for the extensive reference he makes to the best doctrines of others and the often successful attempt to provide a general framework for canonistic juridical science across various subjects up to his time. Where he expresses his own thesis, he reinforces it with strong intellect and great diligence.
His output unfolds especially through commentaries on the various collections of Decretals.
His first commentary was composed on the *Liber Sextus* of Boniface VIII, a youthful work which he himself later corrected with subsequent additions, and the definitive version appears to have been completed before the death of Boniface VIII (1303). This commentary came to be regarded as the *glossa ordinaria* to the *Liber Sextus*, preferred over other commentaries written directly into the text.
Next, in chronological order, came his *Commentaria novella* on the Decretals of Gregory IX, compiled no earlier than 1338: an important work in which he reports many opinions of doctors and proposes his own resolutions with refined intellect. To the same Gregorian Decretals he appended his *Casus breves*. He then wrote a *Lectura in librum sextum decretalium*, a work not completed before 1339. To him is also owed the first *Glossa in Clementinas*. Notable as well are his *Quaestiones Mercuriales*, though not always displaying genuine originality. Among his writings there are also works devoted to particular topics, such as his *Lectura super arboribus consanguinitatis et adfinitatis*, which enjoyed wide medieval circulation, and the *Summa de sponsalibus et matrimonio*, a reworking with additions of the work of Giovanni of Cesena or Anguisola.
To him are also attributed various treatises: *De interdicto*, *De consuetudine* (cited in the *Commentaria novella*), and a *Tractatus de renuntiatione beneficiorum*.