1. Introduction  
2. Background  
   2.1 Definition  
   2.2 Related Terms  
   2.3 Types and Properties  
3. PENS Classification Scheme  
   3.1 Precision  
   3.2 Expressiveness  
   3.3 Naturalness  
   3.4 Simplicity  
4. Languages  
   4.1 English-based Controlled Languages  
   4.2 Languages for Comparison  
5. Analysis  
   5.1 PENS Classes  
   5.2 Properties  
   5.3 Design Decisions  
   5.4 Timeline  
   5.5 Evaluations  
6. Conclusions