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Re: I miss tags

From: Brad Appleton <brad_at_bradapp.net>
Date: 2004-09-24 20:38:12 CEST

On Fri, Sep 24, 2004 at 11:54:19AM -0400, Mark Phippard wrote:
> I just don't get this.
> Virtually everyone will concede that Subversion's copies, and CVS tags
> wind up being the same thing.

I guess I haven't seen such agreement/concession. I think
there is a big difference between two different mechanisms
that can each be used to identical effect, versus the
conceptual use and operation of those mechanisms. I think
there is a difference between "same effect/result" versus
the means used to achieve it and the supporting concepts
and mental metaphors that go along with a particular mechanism.

I'm reminded of a discussion in Bertrand Meyer's
"Object-Oriented Software Construction" where he
mathematically proves that two things (I think it was
Genericity and Inheritance) were "equivalent" in that
each could be used to do the other, but then he goes on to
say that its there are different enough both conceptually
and intended operation that its still not only useful and
productive, but even necessary to keep them both instead
of replace one with the other).

> Personally, I think that representing tags as copies is superior because
> it can leverage all of the existing UI. You do not have to invent a
> special UI to access the tags. Anyone that builds a repository browser of
> any kind, can automatically access the same info etc... If you do not
> want tags "cluttering your UI", then spend some more time thinking out
> your layout, as it ought to be fairly easy to deal with this.

Why should I have to spend a lot of time thinking about how
to sweep under the rug the UI representation of something
I didn't want to be part of it in the first place?

You seem to be arguing for the superiority of one
over the other. I think this discussion isn't about
either-or - I don't think people are saying to get rid
of the current implementation. I see them saying there
is another conceptual usage of tags that is imminently
useful and they think it should exist in addition (not
instead of) the "tags as copies" mechanisms because it is
conceptually orthogonal

> I see little benefit in inventing new UI and metadata for features that
> already work well, and are just a bit foreign to users who have used other
> tools.

I don't think the above is the issue at all. I don't
think its that they are used to other tools and just
need to get used to the "Subversion way". I think that,
independent of the tool used, there is a separate concept
of a baseline from the concept of attributes/properties
to represent information other than baseline information
(or in addition to, but not the same as). Some tools have
different mechanisms, others may have one that can do both,
but that doesn't mean it is a conceptual match for each.

One such example would be Promotion-levels associated with
a subset of files (possibly all on the same branch, or
maybe not). Even this fairly straightforward concept is
complementary (rather than equivalent too) baselines or
copies. Different tools and projects may implement it
different ways (for a discussion of at least a half-dozen
of them, see <http://www.cmcrossroads.com/article/32900>).
And that's just one example -- there are loads of others.

So should SVN get rid of its tags-as-copies? Of course
not. I don't think anyone is saying that. Should it adopt
a CVS-style tags instead? I'm not sure anyone is saying
that either. I think their just saying there is this other
use of tags as attributes/properties that is orthogonal
from tags-as-copies and I want to be able to do that too,
and I want to consider it separately in the UI as well
(whether or not the implementation does or not is
another matter :-).

> To me, the only legitimate issue that has been raised is the lack of
> visibility of where something has been copied to. This sounds like a hard
> problem to solve if a O(1) architecture is to remain. I would rather have
> the cheap copies and figure out a way to solve that other problem. I am
> sure someone will think of some way to solve that.
> Mark
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Brad Appleton <brad@bradapp.net> www.bradapp.net
  Software CM Patterns (www.scmpatterns.com)
   Effective Teamwork, Practical Integration
"And miles to go before I sleep." -- Robert Frost
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Received on Fri Sep 24 20:38:38 2004

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