Subject: SDL-News: Broadcast
tariq#erg.abdn.ac.uk
Date: Mon Aug 03 1998 - 08:19:44 GMT
The originator of this message is responsible for its content.
-----From tariq#erg.abdn.ac.uk to sdlnews -----
Dear Anders,
Many thanks for very detailed and useful response. Since SDL is used to describe
the coomunication systems and protocols I had assumed there must be a mechanism
by which it is possible to broadcast a message. There are number of situations
in which it is desirable to broadcast a message to all the process in the system.
For example the protocols we are develpoing in Aberdeen require a message to be
transmitted to all the process and a process makes a decision either message is
addressed to it or not. I belive it is very similar to a packet which transmitted
over the internet and each reciver makes a decision wheather the packet is addressed
to it or not. If packet is addressed to it, the reciver accept a packet and if not
it ignores it.
There are number of other situation where similar behaviour is desirable.
I can imagne that one could device a process in sdl system whose job would be to
transmit a signal in round-robin fashion to all the process in a block. But
a neater solution would be to have a broadcasting mechanism. I do hope
in future the broadcasting machnism is intorduced into SDL!!!!!
Once again many thanks for your and every body's answers.
TARIQ
> From daemon Fri Jul 31 17:16:39 1998
> >From sdlnews-owner#sdl-forum.org Fri Jul 31 17:16:32 1998
> From: anders#cinderella.dk
> To: sdlnews#sdl-forum.org
> Date: Fri, 31 Jul 98 17:14:28 +100
> X-User-Info: 193.3.141.2
>
> The originator of this message is responsible for its content.
> -----From anders#cinderella.dk to sdlnews -----
>
> Dear Tariq
> I would like to elaborate a bit on Oysteins answer:
>
> Yes, it is true that SDL has no mechanism for broadcast.
> The reason is that SDL is intended for describing open systems where
> you dont have full knowledge of what is going on/who are existing in
> the environment. This is very much like with sending e-mails where you need
> the address of
> each of the receivers or need some kind of 'propagation processes' to explode
> and route
> messages further.
>
> This limitation is not only SDL phylosophy. In ODP and CORBA, this is very closely
> related to
> the need for a 'trader', which is a kind of object (a 'phone book') you can
> access to get references to
> objects. Whenever a new process is created or stopped, it is registered in the
> trader my means
> of some signal exchange to keep the trader up-do-date.
>
> So what you need is a trader. To my knowledge, the OPD group already has standardized
> a
> trader written in SDL, but I don't know whether it is feasible to use it.
>
> If you only want to broadcast within the system boundaries, its more feasible
> to define your own
> simple trader process.
>
> The multi-cast mechanism ('VIA ALL') in SDL is a little bit strange and its
> only in special cases it
> is useful. Its a short-hand notation for sending a signal to each of the blocks
> in a block set. This
> means that you wont hit all the processes in each block - only one process.
>
>
> I hope that this info can be of more help
>
> Regards Anders
> Cinderella I/S
>
> -----Oprindelig meddelelse-----
> Fra: tariq#erg.abdn.ac.uk [SMTP:tariq#erg.abdn.ac.uk]
> Sendt: 29. juli 1998 15:47
> Til: sdlnews#sdl-forum.org; mscnews#sdl-forum.org; oystein.haugen#ericsson.no
>
> Emne: SDL-news: Broadcast
>
> The originator of this message is responsible for its content.
> -----From tariq#erg.abdn.ac.uk to sdlnews -----
>
>
> 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.
>
>
> TARIQ
>
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