  A definition of a quantum vertex algebra, which is a deformation of a vertex
algebra, was proposed by Etingof and Kazhdan in 1998. In a nutshell, a quantum
vertex algebra is a braided state-field correspondence which satisfies
associativity and braided locality axioms. We develop a structure theory of
quantum vertex algebras, parallel to that of vertex algebras. In particular, we
introduce braided n-products for a braided state-field correspondence and prove
for quantum vertex algebras a version of the Borcherds identity.
