Draft for 3.7, 3.8 or 4.x ? ...

Rationale

There are a number of properties we currently use which could be "standardized". In order to avoid conflicts with user defined (custom) properties, these would need to be prefixed or namespaced(*). This would particularly apply to properties used outside of templates, i.e in actions or tags, for example the infamous hideInNav property.

* I don't know how exactly using a namespace would be different, but it seems more elegant than a prefix.