The tree is close to the DocBook Model. The diagram shows the hierarchy of the DocBook components (original DocBook labels/usages in upper case) and the way that structure is used in the IBDH database (labels/usages bracketed in lower case).
The DocBook SET is the parent of all of the individual language versions, each of which is a BOOK. BOOK is the root component in the database so there is one root for each language version. Everything below BOOK is stored as a COMPONENT in the database, identified by its COMPONENT TYPE. There are database-based rules for deciding the component types which a component of a particular type may add as children. Each component has a Common Component ID which points back to the identifier of the corresponding component in the English language version. The actual data for the elements are stored in a one-to-many relationship in a Component Data table, allowing us to store more than one version of each datum (for version control purposes). All data are stored as Unicode. Version control is included within the structure. The DocBook DTDs are reasonably close to our needs. Later, when we have decided on layouts, fonts, etc., they can be customized fairly simply so that we can generate prototypes for the browser-readable and printed outputs.