ATTACH ---+-> attach-string-literal ----+->
            +-> <attach-parameter> -------+
            +-> <attach-parameter-marker> +

  attach-string-literal =

  --> ' --> attach-expression --> ' -->

  attach-expression =

  -+------------------++-> FILENAME -> '<attach-spec>' -+-+
   +-> ALIAS <alias> -++-> PATHNAME ->  <path-name> ----+ |
   +------------------------------------------------------+
   ++------------------------+----------------------------+
    +--> literal-user-auth --+                            |
   +------------------------------------------------------+
   ++-----------------------------+------------------------>
    +-+-+-> database-options --+-++
      | +-> attach-options ----+ |
      +----------- <-------------+

  literal-user-auth =

  ---> USER '<username>' -+------------------------+-->
                          +-> USING '<password>'  -+

  attach-spec =

  --+----------------+-> <file-spec> ----->
    +-> <node-spec> -+

  node-spec =

  -+-> <nodename> -+-------------------+-+->
   |               +-> <access-string> + |
   +------------------ :: <--------------+

  access-string =

  -+-> " <user-name> <password> " --+->
   +-> " <VMS-proxy-user-name> " ---+

  database-options =

  --+--> ELN ---------------------+-->
    +--> NSDS --------------------+
    +--> rdb-options -------------+
    +--> VIDA --------------------+
    +--> VIDA V1 -----------------+
    +--> VIDA V2 -----------------+
    +--> VIDA V2N ----------------+
    +--> NOVIDA ------------------+
    +--> DBIV1 -------------------+
    +--> DBIV31 ------------------+
    +--> DBIV70 ------------------+

   rdb-options =

   -+-> RDBVMS --+-->
    +-> RDB030 --+
    +-> RDB031 --+
    +-> RDB040 --+
    +-> RDB041 --+
    +-> RDB042 --+
    +-> RDB050 --+
    +-> RDB051 --+
    +-> RDB060 --+
    +-> RDB061 --+
    +-> RDB070 --+
    +-> RDB071 --+

  attach-options =

  -+-> DBKEY -+-> SCOPE IS -+-> ATTACH -------+-----------------------+->
   +-> ROWID -+             +-> TRANSACTION --+                       |
   +-> MULTISCHEMA IS -+-> ON --+-------------------------------------+
   |                   +-> OFF -+                                     |
   +-> PRESTARTED TRANSACTIONS ARE -+-> ON --+------------------------+
   |                                +-> OFF -+                        |
   +-+-------+-> RESTRICTED ACCESS -----------------------------------+
     +-> NO -+