  We prove local well-posedness for the Cauchy problem associated to
Korteweg-de Vries equation on a metric star graph with three semi-infinite
edges given by one negative half-line and two positives half-lines attached to
a common vertex, for two classes of boundary conditions. The results are
obtained in the low regularity setting by using the Duhamel Boundary Forcing
Operator, in context of half-lines, introduced by Colliander, Kenig (2002),and
extended by Holmer (2006) and Cavalcante (2017).
