For a valve train development, many information are needed to describe the valve train design. In CDS, all data is stored in so called session files, which can be defined by the user. For the most commonly used valve train designs, pre-defined session files are already available. These session files can be compiled in an user-defined way. A session file is a collection of file pointers to the actual data in the current valve train design. Due to that method, the user can easily modify data for parameter studies.

A session file to completely define a valve train comprises:
- File name Approximation File (Valve Motion law)
- File name valve train geometry
- File name valve spring property file
- File name crank train (distance piston <-> valve)

Thus is that-valve-floated completely described.

A typical session file could look like the following: C:\All_Users\Demosh_TK.APA C:\All_Users\Demosh_TK.Par C:\All_Users\demo.fda C:\Projects\STST.eng
The session file is in generated in ASCII format and can be opened with any available editor.