seqdiag {
      node_width = 100;
      edge_length = 150;

      "Client"
      "Tacker-server"
      "Tacker-conductor"
      "Heat"

      "Client" -> "Tacker-server"
        [label = "POST /vnf_instances/{vnfInstanceId}/instantiate"];
      "Tacker-server" -> "Tacker-conductor"
        [label = "instantiate"];

     ... ------------- Omitted from description ------------- ...

      "Tacker-conductor" -> "Heat"
        [label = "POST stacks"];
      "Tacker-conductor" <-- "Heat"
        [label = "201 Created"];

      === start of the checking of the resource status ===

      === loop start (Repeat until 'CREATE_COMPLETE')===

      "Tacker-conductor" -> "Heat"
        [label = "GET stacks/{stack_name}"];
      "Tacker-conductor" <-- "Heat"
        [label = "302 Found"];

      "Tacker-conductor" -> "Heat"
        [label = "(Redirection) GET stacks/{stack_name}/{stack_id}"];
      "Tacker-conductor" <-- "Heat"
        [label = "200 OK"];

      === loop end ===

      === end of the checking of the resource status ===

    }