Which command and statement inputs are possible depends on the contents of the syntax files assigned. The activated syntax files are searched in the order user syntax
file 
group syntax file 
system syntax file.
The definitions contained in the user syntax file have priority over those in the group and system syntax files. If a definition is contained in several user syntax files, the definition in the last activated user syntax file has priority.
The definitions of BS2000 commands (implemented via system modules) contained in the user syntax files must be accommodated in full by the group or system syntax file. If such a command is defined in all three files, the definition in the user syntax file must be accommodated in full by the group syntax file.
The definitions contained in the group syntax file have priority over those in the system syntax file. Definitions not contained in the group syntax file are taken from the system syntax file. If the file hierarchy was disabled during assignment of a group syntax file, the available command/statement set is based exclusively on the group syntax file.
If a definition is contained in several system or subsystem syntax files, the definition in the last activated subsystem syntax file has priority.
Figure 49: How SDF works when different syntax file types are activated