This diagram shows a "flattened" representation of an entry, where attributes defined in ExtensionModules are first-class attributes of the entry itself -- instead of being "referenced by" or "linked to" an entry, they are actual attributes of Entry.

content and BiblioGraphy show a container relationship with Entry, where the entry can have zero, one, or more of groups of related attributes.

This style of model is characteristic of [WWW]AssociativeDataModels, dynamic languages, and XML, in contrast to [WWW]RelationalDataModels and static languages. See also [WWW]dynamic and static languages.

Here's a one page [WWW]comparison of data models.

Yes, thanks. You're pointing out that the entry has a number of attributes that it "owns" and a number of other attributes that hold relations to other entities.