OpenROAD supports structured data in the form of user classes and user class arrays. A user class is analogous to a row of data with a well-defined set of column types, and a user class array is analogous to multiple rows of data with the same column types.

OpenROAD user classes and user class arrays can be nested to any number of levels, allowing the construction of very complex hierarchical data structures to be passed as parameters to remote 4GL procedures.