Universal vs project-focused

 One of the basic considerations when starting to design an i2b2 project ontology is the primary target audience.

Depth of the navigation

In most cases, it is adviceable to just stick to the original depth of navigation. Depending on the source format the data came from, this can lead to very deep hierarchies. Examplary for an ODM import, one will find seven levels of hierarchy for a clinical trial:

• Study

• • MetaDataVersions

• • • Events

• • • • Forms

• • • • • ItemGroups

• • • • • • Items

• • • • • • • CodeLists

This 

Splitting large value sets without natural hierarchy

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