Forum OpenACS Q&A: error when adding task in work flow building

I am a new user to this community. I am having an error while adding a new task to a sample work flow, I am building.

The error is as follows
***********************************
Required switch -taken_names not provided
    while executing
"wf_make_unique__arg_parser"
    (procedure "wf_make_unique" line 1)
    invoked from within
"wf_make_unique -maxlen 100 \
"
    (procedure "wf_add_transition" line 4)
    invoked from within
"wf_add_transition  -workflow_key $workflow_key  -transition_name $transition_name  -role_key $role_key  -trigger_type $trigger_type  -estimated_minute..."
    invoked from within
"set transition_key [wf_add_transition  -workflow_key $workflow_key  -transition_name $transition_name  -role_key $role_key  -trigger_type $trigger_typ..."
    ("uplevel" body line 51)
    invoked from within
"uplevel {
          ad_page_contract {
    Add task.
} {
    workflow_key:notnull
    transition_name:notnull
    role_key:allhtml
    trigger_type:notnu..."
    (procedure "code::tcl::/web/vsacs/packages/acs-workflow/www/admin/task-a..." line 2)
    invoked from within
"code::tcl::$__adp_stub"
    invoked from within
"if { [file exists $__adp_stub.tcl] } {

      # ensure that data source preparation procedure exists and is up-to-date
      adp_init tcl $__adp_stub
..."
    ("uplevel" body line 3)
    invoked from within
"uplevel {

    if { [file exists $__adp_stub.tcl] } {

      # ensure that data source preparation procedure exists and is up-to-date
      adp_init t..."
    (procedure "adp_prepare" line 2)
    invoked from within
"adp_prepare "
    (procedure "template::adp_parse" line 30)
    invoked from within
"template::adp_parse [file root [ad_conn file]] {}"
    (procedure "adp_parse_ad_conn_file" line 7)
    invoked from within
"$handler"
    ("uplevel" body line 2)
    invoked from within
"uplevel $code"
    invoked from within
"ad_try {
    $handler
      } ad_script_abort val {
    # do nothing
      }"
    invoked from within
"rp_serve_concrete_file [ad_conn file]"
    (procedure "rp_serve_abstract_file" line 60)
    invoked from within
"rp_serve_abstract_file "$root/$path""
    ("uplevel" body line 2)
    invoked from within
"uplevel $code"
    invoked from within
"ad_try {
    rp_serve_abstract_file "$root/$path"
    set tcl_url2file([ad_conn url]) [ad_conn file]
    set tcl_url2path_info([ad_conn url]) [ad_conn path_inf..."
*************************************

any ideas????

Thanks,
Vishal