From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Masterson <dsmasterson@outlook.com>
Subject: Re: CUSTOM_ID vs ID
Date: Mon, 29 Jul 2019 04:23:18 +0000
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In-Reply-To: <87k1c2mvfq.fsf@nicolasgoaziou.fr> (Nicolas Goaziou's message of
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To: Nathan Neff <nathan.neff@gmail.com>
Cc: emacs-orgmode <emacs-orgmode@gnu.org>

Nicolas Goaziou <mail@nicolasgoaziou.fr> writes:

> Nathan Neff <nathan.neff@gmail.com> writes:
>
>> I've often been confused why org-mode has both a CUSTOM_ID
>> and a ID property.  I mean, why not just use one or the other name?
>
> Custom ID are user-defined, and only meaningful in the scope of the
> document. Also, they may appear as-is when exported, e.g., as an anchor
> in HTML.
>
> ID are (or should be) generated by Org, and are valid across files,
> which means they need to be absolutely unique.

Can you talk a little bit about how IDs are generated so that they are
absolutely unique?

> Org keeps track of ID if `org-id-track-globally' is non-nil (the
> default). If this is nil, there is almost no difference between ID and
> custom ID.
>
>> When would I ever have both an ID and a CUSTOM_ID property for
>> a heading?
>
> You may want to refer to a heading from anywhere with id:... but need
> a clean anchor in HTML export, for example.

IDs sound like something that would be useful for synchronizing
information between two (or more) separate Org systems - the ID could be
updated whenever a change occurs and then used to determine what needs
synchronization.  True?
--
David