a

class dnsmasq {
  include dnsmasq::install
  include dnsmasq::config
  include dnsmasq::service

  Class['dnsmasq::install'] -> Class['dnsmasq::config'] ~> Class['dnsmasq::service']
}

b

class dnsmasq {
  class { 'dnsmasq::install': }
  -> class { 'dnsmasq::config': }
  -> class { 'dnsmasq::service': }
}

c

class dnsmasq {
  class { 'dnsmasq::install': }
  class { 'dnsmasq::config': 
    require => Class['dnsmasq::install'],
    notify  => Class['dnsmasq::service'],
  }
  class { 'dnsmasq::service': }
}