Rationale.  
 
Throughout this document, the rationale for the design choices made in  
the interface specification is set off in this format.  Some readers may  
wish to skip these sections, while readers interested in interface design  
may want to read them carefully.  
 ( End of rationale.) 
 
 
 
 Advice to users.  
 
Throughout this document, material aimed at users and that illustrates  
usage is set off in this format.  Some readers may  
wish to skip these sections, while readers interested in programming in  MPI  
may want to read them carefully.  
 ( End of advice to users.) 
 
 
 
 Advice  
        to implementors.  
 
Throughout this document, material that is primarily commentary to implementors  
is set off in this format.  Some readers may  
wish to skip these sections, while readers interested in   
 MPI implementations may want to read them carefully.  
 ( End of advice to implementors.)