trait DB { def startDB: Unit }  // defines an abstract start for a DB component
trait MT { def startMT: Unit }  // defines an abstract start for an MT component

trait Oracle extends DB { def startDB = println("Starting Oracle") } // Some actual concrete instances.. dummied for example
trait Service extends MT { def startMT = println("Starting Service") }

trait App {
    self: DB with MT => // declare that self for App refers to a DB with MT, so that we have access to the startXX ops

    startDB
    startMT
}

object DummyApp extends App with Oracle with Service // create a concrete instance with an actual DB and MT instance
DummyApp.run // run it and see "Starting Oracle" then "Starting Service"