Hi Georg,

I's suggest you have a check at :

1) this blog post, you could find information specific to RPE and RQM with step-by-step guidance
  
   You'll see that the included MindMap provided RPE specific information
   (unfold "[sub-domain] Document Generation (RRDG - RPE) > Rational Pusblishing Engine (RPE)" nodes)
   - as for today - (this information is regularly updated), the enclosed "How to ?" examples / Tips / related blogs" gives you these interesting resources links:

• [Jazz.net wiki] RQM Reportable REST API
• [Jazz.net article] "Compose and execute RPE (1.1.2.2) reports against RQM 4.0" by Y. C. Yuan (Oct 2012)
  
• [Blog] "Extract test case results from RQM with RPE 1.1.2" (May 2012)
  

2) the great source of information (again with step-by-step guidance) provided by the "Reporting Workshop for CLM 4.0.1"
 
Regards,
Stéphane