OK, Mrs. Zabach kindly advised me to use the "user"-special register to find out the current user.
My goal was to create a view which only displayed a selection of a table depending on the logged in user, say
 
CREATE VIEW V_ADRESSES
AS 
SELECT * FROM T_ADRESSES WHERE ADR_SHORT = USER
 
This view is being created without problems, but it never returns results.
If I hardcode the WHERE-clause, it works flawlessly, but with user, I never get results.
 
What's my mistake?
 
Thank you in advance
Marco