SDEdit, sequence diagrams

trying to practice the SDEdit (my previous post here)

Unfortunately I understand stuff only "In Action" and "A step at a time", and I believe in documentation embedded in the code.
So here is my attempt to bring some light into the SDEdit notation.

http://sdedit.sourceforge.net/index.html


#the # is a comment
#the #! is a title
#![SD ticket order]

#this section declares Objects, with Syntax <name>:<type>[<flags>] "<label>"

#flag p means process, e means external
#flag x means auto-destruction
ext:External[pe]
user:Actor "JohnLennnon"
/order:Order[x] "MyOrder"
db:TicketDB
acc:Account

ext:=user.order a ticket!
user:order.new()
#<caller>[<s>]:<answer>=<callee>[m].<message>
order:return=db.reserve(date,count)
db:return=acc.debit(cost)
acc:return=db.bonus(date,count)