 
  
  all:
  hosts:
    host1:
      ansible_host: 192.168.1.1
    host2:
      ansible_host: 192.168.1.2
    host3:
      ansible_host: 192.168.1.3
    host4:
      ansible_host: 192.168.1.4
  children:
    hostSRV:
      hosts:
        host1:
        host2:
        host3:
    hostDB:
      hosts:
        host3:
    hostWEB:
      hosts:
        host1:
        host3: