YES

1 decompositions
 #0 -----------
   1: f(x1,g(x2)) -> f(x1,g(x1))
   2: f(g(y1),y2) -> f(g(y1),g(y1))
   3: g(a()) -> g(b())
   4: b() -> a()

@Development Closedness
--- R
   1: f(x1,g(x2)) -> f(x1,g(x1))
   2: f(g(y1),y2) -> f(g(y1),g(y1))
   3: g(a()) -> g(b())
   4: b() -> a()

--- S
   1: f(x1,g(x2)) -> f(x1,g(x1))
   2: f(g(y1),y2) -> f(g(y1),g(y1))
   3: g(a()) -> g(b())
   4: b() -> a()