A TryTask encapsulates a task. It is useful in case your task may fail and you want to provide some alternative output when it does.
To encapsulate a task in a TryTask, simply wrap it in the TryTask builder:

val result = Val[Double]

val t1 = ScalaTask("val result = someProcessThatMayFail()") set (
  outputs += result
)

TryTask(t1) set (
  result := 10.0 // Value of result in case t1 fails
)

A RetryTask encapsulates a task. It is useful in case your task may fail and you want to retry to execute them multiple times.
To encapsulate a task in a RetryTask, simply wrap it in the RetryTask builder:

val result = Val[Double]

val t1 = ScalaTask("val result = someProcessThatMayFail()") set (
  outputs += result
)

RetryTask(t1, 5) // retry t1 5 times in case of failure