Talk:Q21199

Ambiguity

Note the ambiguity as to whether or not the natural numbers include zero. It would be best if we had other items that were unambiguous about this, perhaps "non-negative integer" and "positive integer" would be appropriate here? —SamB (talk) 14:14, 15 April 2015 (UTC)

And what should we do with sitelinks? Separate? It's not convenient. In Russian we describe both approaches equally, for example. --Infovarius (talk) 07:42, 29 February 2016 (UTC)

Natural numbers are both cardinal numbers and ordinal numbers

Natural numbers, numbers used for counting and ordering, are both cardinal numbers and ordinal numbers: ordinal number (Q191780) should also be a parent class. Tentacles (talk) 20:27, 23 March 2016 (UTC)

P.S. I'm logged in (through Wikipedia): can [[User:Tentacles]] and [[User_talk:Tentacles]] be redirected to the same on Wikipedia. Tentacles (talk) 20:36, 23 March 2016 (UTC)

OEIS ID (P829)

Hi! I wondered that no OEIS ID (P829) is present here.
Regards no bias — קיין אומוויסנדיק פּרעפֿערענצן — keyn umvisndik preferentsn ^{talk contribs} 09:15, 22 July 2019 (UTC)

• This term is ambiguous, so it would probably be better to use positive integer (Q28920044) and non-negative integer (Q28920052) instead. Wikisaurus (talk) 00:05, 5 December 2019 (UTC)

Disjoint union of primes and composite and 1

@慈居, Infovarius: I propose to remove the statement because :

1. this item is ambiguous about the presence and abscence of zero
2. "1" should be for that to work the "singleton" one, N = {1} union prime numbers union composite numbers
3. The qualifier « "applies to part" item i » makes clear that the statement belongs in … item i, not this one ?

Comments on this ? author  TomT0m / talk page 13:41, 7 April 2024 (UTC)

I think I agree with you on this. This item is about a terminology, not a particular notion it can mean, nor a class which has positive and nonnegative integers as instances. I'd prefer to remove those statements which only make sense when it is specified in which sense the term is used. 慈居 (talk) 14:08, 7 April 2024 (UTC)

I went on and I moved the statements to the two precise items. author  TomT0m / talk page 18:26, 7 April 2024 (UTC)

Agree with 1. Not sure about 2. Don't we talk about numbers rather than sets? --Infovarius (talk) 12:17, 8 April 2024 (UTC)

I think what the author tries to say is that "disjoint union of" should be followed by classes, even if the class consists of one instance. 慈居 (talk) 12:36, 9 April 2024 (UTC)

@Infovarius You can't union numbers and sets. prime number is a class, with many instances (like "3" who is a prime number). An union operation is between sets (classes in our case) and you can't union "1" and "primes". You have to make a set with the individuals, and that's what singleton are for. author  TomT0m / talk page 17:05, 9 April 2024 (UTC)

Yes, I understand this, but do we really need classes in this place? Now the claim looks like "natural number can be {1} (singleton class) or primes set or composites set" while for me it would be better "natural number can be 1, prime number or composite number". Infovarius (talk) 08:17, 11 April 2024 (UTC)

@Infovarius This is not what "union" means and is intended for, it's intended to work as working on classes. It's intended to mean "any instance of this class is an instance of at least one of the listed class".

It works for numbers here only because we can assimilate "instance of" to set membership and the "class" notion in ontology to the set/class notion in set theory. Constraints and queries based on "union of" and "disjoint union of" works by assuming everything in the statement are classes. There is one that checks that "1" is a subclass of "integer", but it is an instance, so this does not work.

it's a minor point, but if you do that you introduce an ambiguity considering the number encoding in set theory, as a number is the set of its predecessors. So "1" in encoded as "{0}", and "0" as the empty set "{}", so this gets even more confusing. So if we continue the analogy we get 0 instance of 1. We do not do that, and we should not for obvious reasons, but maybe you can see why it adds confusion here … if you use "1" in a union statement this would mean "{0}". author  TomT0m / talk page 08:43, 11 April 2024 (UTC)

By the way, should we create an item for the "Wikidata class" 1, like in singleton of 0 (Q47342419) and 0 number class (Q30027695)? 慈居 (talk) 11:27, 11 April 2024 (UTC)

@慈居 I think they are duplicates and that we should merge them actually. author  TomT0m / talk page 11:37, 11 April 2024 (UTC)