How do you feel about not creating database tables for objects that only exist in relations?

For example, I have made a wiki engine. Because nothing on wiki pages can actually change, they aren't an entity. Revisions are an entity, and they refer to the title of the page which was changed. The same application also includes two non-version-controlled directed graphs between the pages (element of category and navigation log), which are represented by tables that link two titles. Of course the indexes are all set up so that it works like a foreign key would, but there is no Page or Article table.