Relation is an API module and storage model for both simple and the most complex relations between entities. The module can handle both directional and symmetrical relations very well.
Relations are entities and can therefore have fields. This makes Relation the most flexible and powerful relation model out there. (Still, using Relation with anything but the default SQL storage will not work in most cases.)
The central government of the Netherlands has a standard Visual Identity that is used on every website. The so-called Rijkshuisstijl (central government visual branding) has been translated into this Rijkshuisstijl theme.