SDL-News: Re: Broadcast

Subject: SDL-News: Re: Broadcast
From: Oystein Haugen (
Date: Thu Jul 30 1998 - 07:31:16 GMT

The originator of this message is responsible for its content.
-----From Oystein Haugen <> to sdlnews ----- wrote:

> Can Anybody tell me how to broadcast a signal in SDL. i.e if a system
> is comprised of more
> than one process how can a signal be received by all the processes or
> in other words
> how can a signal be transmitted on more than one channel
> simultaneously.
> YOur answer would be highly appreciated.

Hello Tariq

You should get hold of a copy of the standard Z.100 from ITU.
I quote here from the Z.100 of 1992 about Output:

<output> ::=
  output <output body>

<output body> ::=
  <signal identifier>
  [<actual parameters>]{, <signal identifier> [<actual parameters>]}*
  [to <destination>] [ via [all ] <via path> ]

<destination> ::=
  <PId expression> | <process identifier> | this

<via path> ::=
  <via path element> {, <via path element>}*

<via path element> ::=
   <signal route identifier>
      | <channel identifier>
  | <gate identifier>



If several pairs of (<signal identifier> <actual parameters>) are
specified in an <output body> it is derived syntax for specifying a
sequence of <output>s or <output area>s in the same order specified in
the original <output body> each containing a single pair of (<signal
identifier> <actual parameters>). The to clause and the via clause are
repeated in each of the <output>s or <output area>s.

Stating via all is derived syntax for multicasting the signal via the
communication paths mentioned in <via path>, so that signals are sent in
the same order as <via path element>s appear in <via path>, one via each
<via path element>. Multicast denotes a sequence of outputs of the same
signal. The values conveyed with each of the resulting signal instances
are only evaluated once before interpreting the first output, implicit
variables are then used to store the values for use in each output. If
same <via path element> appears several times in a <via path>, one
signal is sent for each appearance.

Stating this is derived syntax for denoting as <process identifier>,
the implicit <process identifier> for the set of instances of which the
process executing the output is a member.


As you can see from the above quotes, SDL does not have any broadcast
mechanism, but a multicast feature.

Oystein Haugen

Oystein Haugen, Ericsson as. , P.O. box 34, N-1361 Billingstad, Norway
Tel: +47 66 84 23 46 Fax: +47 66 84 19 15 Mob: +47 913 90 914

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