Re: base

[Uday S Reddy <u.s.reddy@cs.bham.ac.uk>]

On 8/26/2010 6:37 AM, Eli Zaretskii wrote:

> Exactly right!  So a document that describes to me how bzr stores its
> metadata in a repository is not the only or necessarily the best way
> of letting me form a model of bzr that is useful enough to guide me in
> day-to-day operations.  For complex and unconventional workflows, it
> _might_ be necessary to use the history DAG to explain them, but for
> the common workflows even that should not be necessary.  And _none_ of
> the workflows really need any description of how the data is stored
> and what algorithms are used to process that data.

Eli, I agree with the general thrust of your argument.  The conceptual model 
you present to the users can be quite divorced from the implementation.  But 
different conceptual models can have different levels of conceptual efficiency. 
  One model might lead you to draw the right conclusions and another might 
mislead you.  This kind of thing is called "representation bias" in Computer 
Science.

I believe that the DAG view is the right conceptual model for version 
management, not the linearized history with time travel as presented by 'bzr 
log'.  When you look at a history like

    429
       326.1.2
       326.1.1
    428

you are not supposed to think "what has changed from 428 to 326.1.1?"  You are 
really supposed to think "what has changed from 326 to 326.1.1?"  The fact that 
326.1.1 is a successor to 326, and *not* a successor to 428, is quite 
important.  The fact that there isn't a single Bazaar document that mentions 
DAG is astonishing.  And, I didn't think of it either until Stephen put a DAG 
in front of me and said "look".  Problem solved.

>> Since you said you had a degree in physics, think of it in those terms:
>
> Physics is an inappropriate analogy here, because physics is not a
> device to be used.  Physics is essentially a body of knowledge and a
> set of rules to extend that knowledge.  Therefore, a physicist is much
> more like a software developer than a software user, and there's
> little surprise that physicist's activities do require the kind of
> under the hood information akin to what the cited Web pages provide
> for git and hg.

This is open to question.  I might argue that a physicist is a user of nature, 
not a developer of nature.  And, the physicist's models ("theories" in their 
terminology) are just conceptually-efficient models of nature.  They are not 
necessarily how things work.  In Quantum Mechanics, for instance, we have no 
real idea how things work, and there are two conceptual models one might use. 
Since it is incoherent to talk about two conceptual models, standard Quantum 
Mechanics text books present neither, which drives the Physics students nuts 
just like the Bazaar documentation drives us nuts.  Physics teachers help out 
by telling students their favorite model, which might appeal to some students 
and not to others.  My teachers always seemed to prefer the particle model.  I 
prefer the wave model myself.  I think it is conceptually efficient.

>> It sometimes takes a little extra effort for the user to learn a model
>> instead of a rote list of actions, but it pays back hugely in giving the
>> user power over his tool.
>
> Agreed; however, existence of such an information should not be
> declared as a fatal blow to the ability of users to learn to use a
> tool safely and efficiently.  It is a bonus, but not a necessity.

Without a good conceptual model, it is doubtful if they can use it "safely and 
efficiently."

Cheers,
Uday