A TCAD system is said to have a dedicated data level if there exists a unified format, representation or procedural interface for the description of simulation data which is sufficiently independent of the tool that has created the data. In other words, an application which consumes data does not have to know which application created the data and an application which produces does not have to take into account which applications will use the data.
A data level can hence be implemented either by 
point-to-point
data converters or by a standardized data representation. A static data
representation is usually accompanied by a procedural interface for
data access.
A point-to-point converter implementation is accepted as a valid ``data level'', as most existing TCAD systems employ mixed forms of standardized representation data levels combined with data conversion (especially when foreign simulation tools are integrated) and a clear distinction between ``proper and improper'' data levels can hence not be made. Moreover even rigorously standardized data levels require occasional high-level converter functionality when certain semantical gaps between independently developed simulators arise (e.g. when different grid types are used). This makes a reliable classification of the data level even more difficult.
The prevailing (de-facto standard) data level architecture is a file-based coupling of simulation tools, using one or more files with a standardized format and agreed semantics.