Property talk:P45

Is this equivalent to Wikidata "logical implication"

Implication is one of the most expressive tools we have on Wikibase. However its current description is brief and we have not linked it to a Wikipedia equivalent. Does A implies K=V (.. assuming W is unequal to V)

1. .. set a default for K which can be overwritten by W?
2. .. mean that combining A with K=W is logically invalid
3. .. mean that combining A with K=W is fine as long as V and W are compatible (like building=religious and building=temple)
4. Does tagging A together with K=V have to be valid tagging (for "man_made=tower implies building=yes" this would not hold)
5. Can A have the same key K, as in "building=religious implies building=yes" or as in the statement "side=both implies side=left as well as side=right".

One candidate for Wikidata equivalent is the logical implication Q374182. Possibly we want to have the ability to express multiple different things (logical implication; setting of a default value) and would need an additional property. —Preceding unsigned comment added by Mapl (talk • contribs) 01:24, 17 January 2026 (UTC)

Why should we even link it to Wikidata or Wikipedia? Can you give me an example of an use-case of such a connection? – With the meaning of P45 I understand the use like in these cases:

• vehicle=yes implies motor_vehicle=yes and bicycle=yes, so you don't need to set the latter ones.
• barrier=fence implies access=no, so you don't need to set the latter one.
• junction=roundabout implies oneway=yes, so you don't need to set the latter one.

Therefore I agree to your points #1 (default which can be overwritten) and #5 (building=* implies building=yes, or side=both implies side=left and side=right. --Chris2map (talk) 08:58, 17 January 2026 (UTC)

I don't think there is a current automation use-case. My use-case is simply to understand what we mean by P45. Putting a clear definition in the property description would work just as well.

Do I understand correctly, especially from your first example, that you interpret P45 as the weaker property of merely setting defaults,? If we agree that tagging "vehicle=yes in combination with bicycle=no" is a good way to tag that all vehicles (motor_vehicles, carriages, ...) except for bikes are allowed, then "vehicle=yes implies bicycle=yes" only makes sense if we interpret P45 as setting a default.

If this is the case, maybe we can make this clear by adding ".. unless otherwise stated".

As this would be different to the logical implication "implies"/"always implies" which could not be overwritten, perhaps we should even find a new title for P45. --Mapl (talk) 11:52, 17 January 2026 (UTC)

I think any ambiguities should best be clarified and documented here in the wiki, by improving the description and possibly creating a separate wiki page for it. – I myself already find it difficult to know when (with which tags) the use or allocation of this property is correct or sensible, and when it is not. Therefore, I would prefer a definition that is as simple and broad as possible. I mean something like: Implies this and that, but can be overridden by other tags. – For major definitional questions or changes, other opinions would be valuable. Talk:Wiki and the community forum would certainly be useful in that case. --Chris2map (talk) 07:31, 18 January 2026 (UTC)