Re: [Monotone-devel] newbie question - SHA1 vs serials

[Timothy Brownawell]

On 4/19/05, K. Richard Pixley <address@hidden> wrote:
>  Jon Bright wrote: 
> >Hi, 
>  Hey.  :-).
>  
>  
> > > To provide globally unique serials, one would need to include some
> > > representation of the location at which an event occurred.
> > It's an idea that's been considered, but has a number of difficulties: 
>  
> > 1. Not everyone's machine has a (valid) domain name.  I have a number of
> > domains, so I could pick one, but if I didn't, the only name I'd have would
> > be p34543522.dip.t-dialin.net or whichever name my ISP gives me today. 
>  This is why I suggested that the repository be named.  Presumably, the name
> would be based on domain name, but the real point is that domain names
> follow hierarchical delegation.

But how is this enforced?

>  
> > 3. I have machine foo.bar.com - what to do about some unpleasant person who
> > decides to incorrectly name their machine foo.bar.com too?  (There are a
> > number of workarounds for this, each with advantages and disadvantages)
>  You do nothing.  It's up to the administrator of bar.com to resolve this
> collision.  Only one of you is actually authorized to use this name. 
> Repository name doesn't necessarily change with IP or domain name change.

But people sometimes do things without being authorized.

>  Now, if you decided to change the name of an existing repository, that
> might represent a potential problem.  The new name would work, but anyone
> who ever tried to reuse the old name would create a collision.  I'm not sure
> this is a problem in practice, though.
>  
> > 4. The number's not actually monotonically increasing when viewing the tree
> > as a whole.  Ignoring branches, I'd still get 
> > 
> > 1:foo.bar.com 
> >       | 
> > 1:baz.foo.com 
> >       | 
> > 2:baz.foo.com [...]
> > 
> > ...which kind-of seems to defeat the point. 
>  The point is two-fold:
>  
>  1) provide human readable visual ordering.  Since global ordering really
> isn't possible, the only ordering that has any meaning is per-repository
> ordering.  And that's what you're seeing.

Might be useful, but couldn't this be done just as well with a "show
ancestry" command?

>  2) providing unique id's.

But only if everyone behaves themselves.

>  I think serials on named repositories do address these points.

This requires some sort of central authority to work. As I understand
it, one of the features of monotone is that there doesn't have to be
any such central authority.

Tim