All the data elements that can be stored in the Clinical Repository must first be defined in a central resource
called the Medical Entities Dictionary (MED). When data are uploaded, local coding schemes are translated into
the central coding schemes (MED codes); when data is retrieved from the Repository, the MED is used to translate
data back into the desired naming scheme. The dictionary solves the "tower of Babel" problem that occurs
when different applications use different names for the same thing. The MED controls the use of data elements within
the institution by defining how variants map onto a single identifier that denotes a unique concept.