From owner-sc22wg5@dkuug.dk Wed Jun 25 21:42:17 2003 Received: (from majordom@localhost) by dkuug.dk (8.12.8p1/8.9.2) id h5PJgHsR061330 for sc22wg5-domo; Wed, 25 Jun 2003 21:42:17 +0200 (CEST) (envelope-from owner-sc22wg5@dkuug.dk) X-Authentication-Warning: ptah.dkuug.dk: majordom set sender to owner-sc22wg5@dkuug.dk using -f Received: from mx2.liv.ac.uk (mx2.liv.ac.uk [138.253.100.180]) by dkuug.dk (8.12.8p1/8.9.2) with ESMTP id h5PJgCEc061323 for ; Wed, 25 Jun 2003 21:42:13 +0200 (CEST) (envelope-from j.l.schonfelder@liverpool.ac.uk) Received: from mailhub3.liv.ac.uk ([138.253.100.83]) by mx2.liv.ac.uk with esmtp (Exim 4.14) id 19VG9f-0003DZ-1T for sc22wg5@dkuug.dk; Wed, 25 Jun 2003 20:42:07 +0100 Received: from localhost.localdomain ([127.0.0.1] helo=mailhub3.liv.ac.uk) by mailhub3.liv.ac.uk with esmtp (Exim 4.14) id 19VG9e-0004oZ-Vr for sc22wg5@dkuug.dk; Wed, 25 Jun 2003 20:42:06 +0100 Received: from vp135021.liv.ac.uk ([138.253.135.21] helo=jls-rm-home.liv.ac.uk) by mailhub3.liv.ac.uk with esmtp (Exim 4.14) id 19VG9e-0004oW-Pf for sc22wg5@dkuug.dk; Wed, 25 Jun 2003 20:42:06 +0100 Date: Wed, 25 Jun 2003 20:42:07 +0100 From: "J.L.Schonfelder" To: sc22wg5@dkuug.dk Subject: Re: (SC22WG5.2819) Directions for Modules TR - levels Message-ID: <23452082.1056573727@jls-rm-home.liv.ac.uk> In-Reply-To: <200306251906.h5PJ6v2U061109@dkuug.dk> References: <200306251906.h5PJ6v2U061109@dkuug.dk> Originator-Info: login-id=jls; server=pop1.liv.ac.uk X-Mailer: Mulberry/2.2.1 (Win32) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline X-Scanner: exiscan for exim4 (http://duncanthrax.net/exiscan/) *19VG9f-0003DZ-1T*LXmll2n2eQA* Sender: owner-sc22wg5@dkuug.dk Precedence: bulk --On 25 June 2003 12:06 -0700 Van.Snyder@jpl.nasa.gov wrote: > > I wrote: > >> > For a large module there may be a need to share entities between >> > procedures in different submodules. With only two levels, the only >> > place to put those shared entities is in the module. This is really >> > part of the implementation. Putting it into the module could cause a >> > compilation/certification cascade as a consequence of changing an >> > implementation detail. So you need at least three levels. Once you >> > have three, there's really no point to a limit, although I doubt in >> > practice we would see more than three. > > and Bill Long replied: > >> I had thought about the issue of sharing things among a group of >> submodules. This seems like something that would be desirable. However, >> I don't agree that the only way to do this is with another layer of >> submodules. The shared stuff can be put in an ordinary module (not the >> parent) that is used by all the submodules in the group. This would >> seem to me the natural thing to do, having used modules in this way for >> a long time. The module with the shared stuff is not a submodule, >> eliminating the need for a third level, and is also unrelated to the >> parent module, so does not affect the key feature of avoiding >> compilation cascades. Is there a flaw in this approach? If not, it >> seems that the simplification that results from just two levels is >> desirable. > > It doesn't work if any of the shared stuff depends on private stuff. > > I'm in Richard's camp on this issue. If we can't think of a really > compelling reason for an artificial restriction, we ought not to have it. > Searching for a reason not to impose an artificial restriction is not > the way I would develop things. I too am very strongly in this camp. Restrictions on an easily generalisable facility are usually undesirable and should be justified by compelling reasons. I see no such reasons in this instance. > > > -- > Van Snyder | What fraction of Americans believe > Van.Snyder@jpl.nasa.gov | Wrestling is real and NASA is fake? > Any alleged opinions are my own and have not been approved or disapproved > by JPL, CalTech, NASA, Sean O'Keefe, George Bush, the Pope, or anybody > else. > > -- Lawrie Schonfelder Honorary Senior Fellow University of Liverpool 1 Marine Park, West Kirby, Wirral, UK, CH48 5HN Phone: +44 (151) 625 6986