Though I agree Daniel with what you wrote about redirects, we do have a policy (I believe I have read this somewhere) that if you create a redirect in the case of two items about the same thing, then it should always be the older item number that survives (and the merge gadget is supposed to check for this). Maybe that's too much detail information though. So for the given example "Moon" was created first and thus it is "Moon" id that should survive, whether or not the label is set to "The Moon" later.

<quote>

Yes, page IDs survive renaming/moving the page.

> 2. What if we have page "Moon" with ID=1. Someone creates a second-page
> "The_Moon" with ID=2. Is it possible that page "Moon" is transformed into a
> redirect? Then, "Moon" would be redirecting to page "The_Moon"?

Yes, pages can become redirects.
</quote>

On Mon, Apr 24, 2017 at 2:04 PM, Daniel Kinzler <daniel.kinzler@wikimedia.de> wrote:
Hello Gintautas!

Am 21.04.2017 um 17:58 schrieb Gintautas Sulskus:
> I have a couple of questions regarding the Wiki Page ID. Does it always stay
> unique for the page, where the page itself is just a placeholder for any kind of
> information that might change over time?

That is indeed the idea. COntent changes, the page ID stays the same. If you
need to identify a specific state of the page, use the revision ID (aka permalink).

Note however that page IDs are considered "internal" identifiers. They are
stable, but they are not the canonical way to access or identify a page. Use the
title for that - or, in the context of Wikidata, use the entity ID.

> Consider the following cases:
> 1. The first time someone creates page "Moon" it is assigned ID=1. If at some
> point the page is renamed to "The_Moon", the ID=1 remains intact. Is this correct?

Yes, page IDs survive renaming/moving the page.

> 2. What if we have page "Moon" with ID=1. Someone creates a second-page
> "The_Moon" with ID=2. Is it possible that page "Moon" is transformed into a
> redirect? Then, "Moon" would be redirecting to page "The_Moon"?

Yes, pages can become redirects.

> 3. Is it possible for page "Moon" to become a category "Category:Moon" with the
> same ID=1?

Yes, pages can be moved into the category namespace.

--
Daniel Kinzler
Principal Platform Engineer

Wikimedia Deutschland
Gesellschaft zur Förderung Freien Wissens e.V.

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