BRF+ Message Log & "Rule as Expression"

Hi colleagues,
I am quite new to BRFplus and have two questions:
1) I would like to use a message log action in order to indicate errors. I tried to follow   with method SET_APPLICATION_LOG_OBJECT, but I can't find the class this method belogns to. I also tried modelling a rule & action message log with help of the UI. My question is how can I log messages and where can I find them after the function is beeing processed?
2) In every guide I can read something about rule expressions and even how to create them (e.g., but in the workbench there is no possibilty of creating rules as expressions but only rules and rulesets (the rule is not part of the "Expression" node).
I hope somebody knows what I mean
Thanks a lot & kind regards,

Thanks a lot for your response!
Could you tell me why using rules and rulesets is not recommended for 7.01 ? This could be interesting for my bachelor thesis.
Thanks & Kind Regards,