User:ChristianKl/Draft:Help:Instance and Subclass

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For users who are new to data-modeling the concepts of instance of (P31) and subclass of (P279) can be confusing. For programmers the notions of object-oriented programming can be helpful.

Notre-Dame de Paris (Q2981) is a particular cathedral (Q2977) that exists in the real world and this is modelled via instance of (P31). On the other hand Diego Velázquez (Q297) is a type of church building (Q16970) which is a type of building (Q41176) which inturn is a type of architectural structure (Q811979). The relationship between those types gets modeled via subclass of (P279).

Given that architectural structure (Q811979) properties for this type (P1963) coordinate location (P625) we can expect that entities that are instances of architectural structure (Q811979) or instances of subclasses of architectural structure (Q811979) like cathedral (Q2977) to be an entity of the kind that has an coordinate location (P625). Notre-Dame de Paris (Q2981) is an entity of the kind that normally has a coordinate location (P625) but cathedral (Q2977) isn't and thus cathedral (Q2977) isn't a subclass of architectural structure (Q811979).

Given that Gutenberg Bible (Q158075) instance of (P31) version, edition, or translation (Q3331189) it is the kind entity that could have an ISBN-13 (P212). The fact that this particular version, edition, or translation (Q3331189) doesn't have an ISBN-13 (P212) as it was published way before the ISBN system was started doesn't invalidate the fact that it's an object of the kind that theoretically have an ISBN in a way that means that church building (Q16970) or cathedral (Q2977) aren't. properties for this type (P1963) suggests that in the normal case we can expect an ISBN-13 (P212) but it's understood that many cases aren't the normal case.