1. Dynamic, asserta, assertz, retract.

• Tutorial material: ( search dynamic, and read the examples)
• http://cs.wwc.edu/~cs_dept/KU/PR/Prolog.html (dynamic x/1 example)
• http://www.guides.sk/prolog/tut/tut16.html (list length count example)
• be sure understand dynamic, assert, retract.

2. Sample.

• pet example