Loading and querying knowledge bases

• Download the knowledge bases kb1.pl, kb2.pl, and kb3.pl (which are the knowledge bases that we just talked about). To download, right click on the following links and choose 'save link to disk'.

  kb1.pl

  kb2.pl

  kb3.pl

• Now type consult('kb1.pl'). at the ?- prompt. This loads knowledge base kb1.pl. Prolog should respond with

  % kb1.pl compiled 0.00 sec, 0 bytes
  
  Yes
  	

• Type listing. to see which facts and clauses Prolog now knows about.
• If you now send queries to Prolog, they will be answered based on this knowledge. Try this. Here are some queries that you could send.

  Is ron a wizard?	wizard(ron).
  Is ron a muggle?	muggle(ron).
  Who is a muggle?	muggle(X).
  Who does crookshanks chase?	chases(crookshanks,X).
  Who chases whom?	chases(X,Y).

• Don't forget to put a full stop at the end of each query before pressing return. If you do forget to put a full stop, Prolog will react by just doing nothing. This is what you will see on the screen:

  ?- wizard(harry)
  |
  	

  To fix it just type a full stop and press return again:

  ?- wizard(harry)
  |    .
  
  Yes
  	

• If something else goes wrong and Prolog start writing crazy things on the screen without getting back to showing you the ?- prompt, type Ctrl-c. This should show you the following line:

  Action (h for help) ?
  

  Type a (for abort) and press return. This should get you back to the ?- prompt.
• Load and query the other two knowledge bases (kb2.pl and kb3.pl), as well. It is probably a good idea to clean Prologs internal knowledge base before loading a new one. The easiest way to do this, is to actually leave Prolog by typing halt. and restart it (by typing pl).
• Play a bit with the knowledge bases kb1.pl, kb2.pl, and kb3.pl, before going on to the next section, which will tell you how to write your own knowledge bases.

Next: Writing knowledge bases.

Back to the practical session of day 1.