Ajutor:What are domains and ranges?
- Question
- question:=What are domains and ranges?
Categories can have properties. For instance, an atom has an atomic weight, which is a number. Atom is the category and atomic weight is the attribute. So each instance of an atom has an atomic weight, e.g. 1.008 for Hydrogen.
Normally it is sufficient, to create a property (e.g. Property:atomic weight) and assign a type to it (e.g.[[has type::Type:float). The problem is, that the property can be used in every article of any category. In consequence, even a car could have an atomic weight.
To find out errors of this kind, the articles for properties should be annotated with a domain and range hint. The article for Property:atomic weight will contain the following line:
[[has domain hint::Category:Atom]]
The domain is the subject of a property, like the grammatical subject in a normal sentence: An atom has an atomic weight.
Properties can have a type like numbers, string, dates etc. or they can have an object, if they are of type page. For instance, a chemical reaction has a product of a molecule. In this case, the property is has product, its subject (domain) is a Chemical reaction (a category) and its object (called range) is a molecule (a category). So the property has product will be defined like this on the page Property:has product:
[[has domain hint::Category:Chemical reaction]] [[has range hint::Category:Molecule]]