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Re: Importing from ClearCase

From: Paul D. Smith
Subject: Re: Importing from ClearCase
Date: 13 Nov 2001 17:41:56 -0500
User-agent: Gnus/5.0808 (Gnus v5.8.8) Emacs/20.7

%% Mark <address@hidden> writes:

  m> The metadata issue really isn't a big issue. You will have to cut
  m> the fat. If the CC metadata can't be converted/used in a productive
  m> way in a CVS, then there is not much you can do about that.

Exactly... and if you need that metadata, then it _is_ a big issue.
Often this metadata is an integral part of whatever SCM process you are
using when you use ClearCase.

  m> The major problem is that CC uses a database for its backend and
  m> CVS uses a flat file directory structure.

Yep, that's why I said:

> Also, obviously things like directory renames, etc. cannot be easily
> handled.

  m> (just curious, I not sure if name metadata in CC is held in the
  m> directory element or not,

It is held in the directory element.  Each version of a directory is
nothing more than a list of links to other elements (note, links to
_ELEMENTS_, not links to _VERSIONS_... often that confuses people).

In fact, elements in ClearCase don't _have_ intrinsic names (just like
files in UNIX); instead, they have unique OIDs.  They only have a given
name because some directory element contains a link to that OID and has
that given name associated with the link.

If you're familiar with how UNIX filesystems work, then ClearCase
directories are very straightforward, logical, and even elegant.  By far
the best implementation of directory versioning I've ever seen.

  m> if you have one file element listed in two different directory file
  m> elements and changed name in one, whould you see the name change in
  m> the other?

No.  You could even have different versions of the _same_ directory
element and change the name in one version, and it wouldn't impact other

  m> even if work continued on that file from both directories?)

Yes... still no.

A directory element just defines which other elements are visible when
you look in that directory.  Your config spec, as always, defines what
_versions_ of those elements you see.

  m> ...

All the problems you discuss are very severe, but they're all derived
from the same issue: ClearCase has directory versioning and CVS doesn't.
If you've done a good bit of renaming/moving in your ClearCase VOB,
you'll have seriously unpalatable choices to make trying to migrate it
to CVS.

 Paul D. Smith <address@hidden> HASMAT--HA Software Mthds & Tools
 "Please remain calm...I may be mad, but I am a professional." --Mad Scientist
   These are my opinions---Nortel Networks takes no responsibility for them.

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