GUIDELINE 6.28
Using System Fields on the User Interface
ABAP_BACKGROUND
As system fields are defined using the syst structure in ABAP
Dictionary, you can technically use them to define input fields in
dynpros/in Web Dynpro.
ABAP_RULE
Do not use system fields on the user interface
Never use system field types to define input or output fields for
dynpros or selection screens in application programs.
ABAP_DETAILS
This rule is derived from the SoC
rule and the use of data types rule .
System fields are purely technical. Their semantic properties, are
defined in the ABAP Dictionary (documentation and other texts), do not
allow meaningful use in the user dialogs of application programs.
Note
Similarly, you can apply the rule only use
semantically appropriate data types to the use of SYST
structure components (for typing interface parameters of procedures).
The semantic meaning of a system field (expressed in the short text)
does not generally match the meaning of the parameter.
Example
When the program
PGL_SYSTEM_FIELD_ON_UI is executed, input fields for document
output language are displayed on a classical dynpro. The first input
field is declared with reference to data type syst-langu of
system field sy-langu . The second input field is declared with
reference to a semantically suitable ABAP Dictionary data type. The
displayed F1 help clearly indicates that syst-langu is not
suited for language fields in a user dialog. This is because the help
only describes the behavior of the sy-langu field in a program.
It does not describe the meaning of the language field in the relevant
application.
Documentation extract taken from SAP system, � Copyright SAP AG. All rights reserved