<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
<HTML>
<HEAD>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
<META NAME="Generator" CONTENT="MS Exchange Server version 5.5.2653.12">
<TITLE>RE: [Modules] Unloading and Conflicting Versions</TITLE>
</HEAD>
<BODY>
<P><FONT SIZE=2>Dave, could you please repost these links? I couldn't find them in the squeak ML archives.</FONT>
</P>
<P><FONT SIZE=2>thank you,</FONT>
<BR><FONT SIZE=2>Rob</FONT>
</P>
<P><FONT SIZE=2>> -----Original Message-----</FONT>
<BR><FONT SIZE=2>> From: Dave [<A HREF="mailto:dave@bedarra.com">mailto:dave@bedarra.com</A>]</FONT>
<BR><FONT SIZE=2>> Sent: Monday, August 20, 2001 9:06 PM</FONT>
<BR><FONT SIZE=2>> To: Les Tyrrell</FONT>
<BR><FONT SIZE=2>> Cc: squeak-dev@lists.squeakfoundation.org; modsqueak@bluefish.se</FONT>
<BR><FONT SIZE=2>> Subject: Re: [Modules] Unloading and Conflicting Versions</FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> 1. The mechanism for unloading is indeed a good deal more complex than</FONT>
<BR><FONT SIZE=2>> loading and was one of the throny problems OTI had to address in</FONT>
<BR><FONT SIZE=2>> building embedded Smalltalk and Java. </FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> Perhaps the issue of unloading is something to be deferred until after</FONT>
<BR><FONT SIZE=2>> the basic module and component mechanisms are defined and tested? </FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> 2. To my knowledge the only existing system that supports current</FONT>
<BR><FONT SIZE=2>> execution of multiple versions classes/methods is MS.NET with their</FONT>
<BR><FONT SIZE=2>> assemblies. This itself gets problematic however if you want to run</FONT>
<BR><FONT SIZE=2>> shared assemblies. I posted the references earlier for those </FONT>
<BR><FONT SIZE=2>> interested</FONT>
<BR><FONT SIZE=2>> in the problem. </FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> Regards,</FONT>
<BR><FONT SIZE=2>> Dave</FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> Les Tyrrell wrote:</FONT>
<BR><FONT SIZE=2>> > </FONT>
<BR><FONT SIZE=2>> > ----- Original Message -----</FONT>
<BR><FONT SIZE=2>> > From: Dan Moniz <dnm@pobox.com></FONT>
<BR><FONT SIZE=2>> > > I'm imagining that when you file in a ChangeSet (let's </FONT>
<BR><FONT SIZE=2>> say Foo.cs)</FONT>
<BR><FONT SIZE=2>> > > into your image (Bar.image), your image is writing out </FONT>
<BR><FONT SIZE=2>> information to</FONT>
<BR><FONT SIZE=2>> > > it's Bar.changes file that reflect the things Foo.cs is </FONT>
<BR><FONT SIZE=2>> doing to your</FONT>
<BR><FONT SIZE=2>> > > image. Then, to back out, you could use a currently </FONT>
<BR><FONT SIZE=2>> fictional "Undo"</FONT>
<BR><FONT SIZE=2>> > > feature which would allow you to back up steps as recorded in</FONT>
<BR><FONT SIZE=2>> > > Bar.changes</FONT>
<BR><FONT SIZE=2>> > </FONT>
<BR><FONT SIZE=2>> > There are a few things that would need to be done when </FONT>
<BR><FONT SIZE=2>> unloading a module. For</FONT>
<BR><FONT SIZE=2>> > one, you would like a rapid way of gc'ing or otherwise </FONT>
<BR><FONT SIZE=2>> mutating any instances</FONT>
<BR><FONT SIZE=2>> > defined by that module. Then, you will want a rapid way of </FONT>
<BR><FONT SIZE=2>> removing the</FONT>
<BR><FONT SIZE=2>> > definitions found in that module. ChangeSets are no </FONT>
<BR><FONT SIZE=2>> better, and no worse, at</FONT>
<BR><FONT SIZE=2>> > doing this than any other scheme. There is no need to </FONT>
<BR><FONT SIZE=2>> iterate over a change</FONT>
<BR><FONT SIZE=2>> > log- the ChangeSet already has an accounting of what it has </FONT>
<BR><FONT SIZE=2>> modified. So would</FONT>
<BR><FONT SIZE=2>> > an OasisModule, or a Collage Layer.</FONT>
<BR><FONT SIZE=2>> > </FONT>
<BR><FONT SIZE=2>> > However, while associating a ChangeSet with either a </FONT>
<BR><FONT SIZE=2>> Collage Layer or an</FONT>
<BR><FONT SIZE=2>> > OasisModule seems reasonable to me, trying to warp </FONT>
<BR><FONT SIZE=2>> ChangeSet into becoming more</FONT>
<BR><FONT SIZE=2>> > like these things does not seem reasonable.</FONT>
<BR><FONT SIZE=2>> > </FONT>
<BR><FONT SIZE=2>> > > This may necessitate modifications to userland tools to </FONT>
<BR><FONT SIZE=2>> deal with</FONT>
<BR><FONT SIZE=2>> > > .changes file, and perhaps some modification to the information</FONT>
<BR><FONT SIZE=2>> > > and/or format of information stored in .changes files, </FONT>
<BR><FONT SIZE=2>> but I don't</FONT>
<BR><FONT SIZE=2>> > > think it would be too drastic and I don't think it </FONT>
<BR><FONT SIZE=2>> would have much</FONT>
<BR><FONT SIZE=2>> > > with the implementation of ChangeSets themselves.</FONT>
<BR><FONT SIZE=2>> > </FONT>
<BR><FONT SIZE=2>> > What's wrong with the idea of implementing the roles of a </FONT>
<BR><FONT SIZE=2>> Components and</FONT>
<BR><FONT SIZE=2>> > Modules? In Oasis, a Module is a component that keeps </FONT>
<BR><FONT SIZE=2>> track of Shared Globals,</FONT>
<BR><FONT SIZE=2>> > Undeclared variables, Pools, and a few other things. </FONT>
<BR><FONT SIZE=2>> ChangeSets don't do this.</FONT>
<BR><FONT SIZE=2>> > </FONT>
<BR><FONT SIZE=2>> > The role of a changeset is to keep track of changes... the </FONT>
<BR><FONT SIZE=2>> role of an</FONT>
<BR><FONT SIZE=2>> > OasisModule is to act as a place in which those changes </FONT>
<BR><FONT SIZE=2>> take effect. These are</FONT>
<BR><FONT SIZE=2>> > separate roles, so I would not reccomend mixing them. </FONT>
<BR><FONT SIZE=2>> ChangeSets are just fine</FONT>
<BR><FONT SIZE=2>> > the way they are, at least in the sense of the scoping of </FONT>
<BR><FONT SIZE=2>> their responsibilities</FONT>
<BR><FONT SIZE=2>> > to tracking changes, and no more.</FONT>
<BR><FONT SIZE=2>> > </FONT>
<BR><FONT SIZE=2>> > Using ChangeSets as a means of identifying chunks of code </FONT>
<BR><FONT SIZE=2>> to turn into a package</FONT>
<BR><FONT SIZE=2>> > is another issue, as far as I know there is nothing wrong with that.</FONT>
<BR><FONT SIZE=2>> > </FONT>
<BR><FONT SIZE=2>> > - les</FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> </FONT>
</P>
</BODY>
</HTML>