  Tensor solutions ($r$-matrices) of the classical Yang-Baxter equation (CYBE)
in a Lie algebra, obtained as the classical limit of the $R$-matrix solution of
the quantum Yang-Baxter equation (QYBE), is an important structure appearing in
different areas such as integrable systems, symplectic geometry, quantum groups
and quantum field theory. Further study of CYBE led to its interpretation as
certain operators, giving rise to the concept of O-operators. In [3], the
O-operators were in turn interpreted as tensor solutions of CYBE by enlarging
the Lie algebra. The purpose of this paper is to extend this study to a more
general class of operators that were recently introduced [4] in the study of
Lax pairs in integrable systems. Relationship between $\calo$-operators,
relative differential operators and Rota-Baxter operators are also discussed.
