Reference edition:

Grammatici Latini, I. Flauii Sosipatri Charisii Artis grammaticae libri V, Diomedis Artis grammaticae libri III, Ex Charisii arte grammatica excerpta, ex recensione H. Keilii, Hildesheim 1961, 299-529 (reprografischer Nachdruck der Ausgabe, Leipzig 1857).

Diomedes’ grammatical treatise is divided into three books, and is also known by the longer title De oratione et partibus orationis et vario genere metrorum libri III. The first book covers parts of discourse, the systems of cases and verbs, and elements of syntax and agreement; the second treats basic concepts of grammar and stylistics; the third deals with meter and poetics, and includes a schematization of literary genres that is considered second only to Quintilian (von Albrecht) and undoubtedly capable of having influenced Medieval Latin epos (Schaller, D’Angelo).  In particular, its treatment of Horatian meters is of remarkable importance for its fullness and accuracy.  Diomedes’ grammar is especially important because it has come down to us intact and fills in those places where the grammar of Charisius is lacunose. Both Suetonius and Varro have been identified among its sources.  [A. Balbo; tr. C. L. Caterine].