Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!gem.mps.ohio-state.edu!apple!voder!pyramid!athertn!joshua
From: joshua@athertn.Atherton.COM (Flame Bait)
Newsgroups: comp.software-eng
Subject: Re: How Do Interface Description Languages Work?
Message-ID: <12697@joshua.athertn.Atherton.COM>
Date: 15 Sep 89 22:45:13 GMT
References: <22096@cup.portal.com> <22121@cup.portal.com> <45a2db57.18268@apollo.HP.COM>
Reply-To: joshua@atherton.com (Flame Bait)
Organization: Atherton Technology, Sunnyvale, CA
Lines: 30

marc@apollo.HP.COM (Marc Gibian) writes:
>One well defined IDL that I have experience with is the Network
>Interface Definition Language, or NIDL, that is part of the
>Apollo NCS product.  NIDL is used to isolate the application
>implementor from the nitty gritty details of using the NCS
>RPC mechanism.  

If you want a better IDL, I'd look at Sun's XDR system.  Unlike NIDL, it
was designed from the begining to be a general purpose data language
(ie. to be used for more than just remote procedure calls).  This difference
in design philosophy shows.  Also, XDR can support any data type used by
C, NIDL can not.  For example, NIDL can not process structures which contain
pointers to structures, except via arcane, complicated functions, which 
you must write yourself.  XDR on the other hand, can handle an entire B-tree
as a single data unit.

Also, XDR is freely distributable, and available from several archive servers
on the net.  This distribution includes the source for an XDR compiler, which
can form the basis for many useful utilities.  You need to pay a little money
for NIDL, and the source code for it is very expensive.

Finally, I'd like to say that I have used NIDL, XDR, and a similar product
from Netwise.  Also, I do not work (and have not worked) for Apollo, Netwise, 
or Sun.

Joshua Levy
--------                Quote: "If you haven't ported your program, it's not
Addresses:                      a portable program.  No exceptions."  
joshua@atherton.com          
{decwrl|sun|hpda}!athertn!joshua    work:(408)734-9822    home:(415)968-3718