coding an Application in perl

Hi,

I'm thinking of writing an/some additional Application/s.
So far one thing puzzles me in the docs:

http://wiki.zmanda.com/index.php/Application_API/Operations
for the output of 'estimate' says block_size is optional, and
if absent, it defaults to:  >>>  1  <<<

In the source amraw.pl, I see the code to output the size,
and it supplies a block size of 1 (the default, I guess), but
it is actually printing the size/1024, so I take it a block
size given as n actually means n K ?

https://github.com/zmanda/amanda/blob/4e02dbe274736c180f0cd8a40d2c5dfe4b2a0b64/application-src/amraw.pl#L158

If that's right, maybe it should be clarified in that wiki page.

Also, the wiki page lists a COLLECTION keyword in the 'support',
but doesn't say anything at all about what it is for or what it
means. The Application_API/Terminology page describes what a
Collection is, but doesn't explain what COLLECTION YES or
COLLECTION NO would mean in an application.

Lastly, the description of the DAR keyword on that page is
sort of mysterious if the reader doesn't already know what
DAR is. What is the best place to look to understand the
feature?  I found a very brief description (good for learning
what it even means, but far too brief to learn anything about
how it works) in a Terminology mailing-list message from 2000:

http://archives.zmanda.com/amanda-archives/viewtopic.php?t=5263&sid=0b9fb71d7e3ed95663fd0c5fd372f48b

And also the commit that implemented it (much more detail on how
it all works, obviously, but a bit much to use as an introduction).

https://github.com/zmanda/amanda/commit/3b8384fc9f2941e2427f44c3aee29f561ed67894

What would be the best place to look for a sort of basic functional
description like "offsets and sizes get stored in the index in
such-and-such a way, and during restoration get fed over the
dar pipe causing such-and-such process to seek...."  Clearly I've
managed to glean that much, but a description that fills in more
of the such-and-suches would probably make a good introduction.

Thanks,
Chapman Flack