This is an example USDA result adding an Specialize Arc to a prim.

#usda 1.0
(
    defaultPrim = "World"
)

def Xform "World"
{
    def Xform "prim" (
        prepend specializes = </World/base>
    )
    {
    }

    def Xform "base"
    {
    }
}