Property talk:P4777

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has boundary
element that's on the two dimensional border that surrounds the subject; the limit of an entity

Description	the element that's on the two dimensional border that surrounds the subject; the limit of an entity
Data type	Item
Domain	geographic location (Q2221906) (note: this should be moved to the property statements)
Example	Old City of Jerusalem (Q213274) → Walls of Jerusalem (Q2918723) Carança valley (Q28380499) → Pic de la Fossa del Gegant (Q3382408) Arizona (Q816) → Arizona–New Mexico border (Q3088721) peritoneal cavity (Q1030169) → peritoneum (Q9629)
Tracking: usage	Category:Pages using Wikidata property P4777 (Q118210312)
See also	shares border with (P47), contains (P4330)
Lists	Items with the most statements of this property Count of items by number of statements (chart) Items with the most statements Items with the fewest statements Count of items by number of sitelinks (chart) Items with the most sitelinks Items with the most sitelinks, but no link to one Wikipedia (sample: Welsh Wikipedia, cywiki) Items with the fewest sitelinks Most linked wikis Items with the most identifier properties By value of property Most statements Fewest statements Most sitelinks Most linked wikis Total of sitelinks on items Most identifiers Fewest identifiers Items with no other statements Most recently created items Items with novalue claims Items with unknown value claims Usage history (total) Usage history (main statement) Chart by item creation date Database reports/Constraint violations/P4777 Map Random list
Proposal discussion	Proposal discussion
Current uses	Total 1,326 Main statement 1,312 98.9% of uses Qualifier 14 1.1% of uses
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[create Create a translatable help page (preferably in English) for this property to be included here]

Allowed entity types are Wikibase item (Q29934200), Wikibase lexeme (Q51885771): the property may only be used on a certain entity type (Help)

Exceptions are possible as rare values may exist. Exceptions can be specified using exception to constraint (P2303).
List of violations of this constraint: Database reports/Constraint violations/P4777#Entity types

Qualifiers “”: this property should be used only with the listed qualifiers. (Help)

Exceptions are possible as rare values may exist. Exceptions can be specified using exception to constraint (P2303).
List of violations of this constraint: Database reports/Constraint violations/P4777#allowed qualifiers, SPARQL

Limited to 2D?

At the moment, I think we don't have to make this poperty limited to the 2D boundary line. Exactly speaking, walls are not 2D, but 3D. And it is very useful if it can also be used to link to 3D boundary surface. For example, many anatomical entities have 3D boundary surface. If necessary in the future, we can create subproperties or use qualifiers to distinguish 2D bounary lines and 3D boundary surfaces. --Okkn (talk) 14:44, 22 January 2018 (UTC)

dimensionalty is tricky. [digs out Euclid] The boundary of a 2-D surface is a line; a line has length without breadth, i.e. a 1 dimensioned thing in 2-D space. Likewise the boundary of a 3-D space is a 2-D surface. Physical boundary markers in the real world, like the walls of Jerusalem, are 3-D. There's no need for this to be a problem if the definition is "the border that surrounds the subject; the limit of an entity". --Philbarker (talk) 16:02, 23 January 2018 (UTC)

@Okkn: A wall around a city doesn't surround most of the 3D surface of the city. It only surrounds a 2D boundary line. Airplanes can fly over the wall of Jerusalem and you can dig tunnels under it. Mixing both things that actually surround all the 3D surface and things that surround an object only in two dimensions in the same property is going to lead to misinterpretation about what's claimed.

That said, things that do surround an object in three dimensions also surround it in two. ChristianKl ❪✉❫ 21:26, 16 February 2018 (UTC)