The DxDataBook view is a layer on top of the Central Library. Basically a parametric database that references to the Central Library using the same part numbers (DEVICE property) and also references the symbols. The database can be Access, Excel, MySQL and other ODBC compliant databases.
So when you search the library with the database view and select a part it fetches the part from the central library and adds properties as appropriate. This is covered in the on-line documentation.