Rule-Based/Expert Systems

Definition of Expert systems are:

– Knowledge based systems
– Part of the Artificial Intelligence field
– Computer programs that contain some subject-specific knowledge of one or more human experts
– Made up of a set of rules that analyze user supplied information about a specific class of problems.
– Systems that utilize reasoning capabilities and draw conclusions.

Terms Associated with Expert Systems
+ Knowledge Engineering – building an expert system
+ Knowledge Engineers – the people who build the system
+ Knowledge Representation – the symbols used to represent the knowledge
+ Factual Knowledge – knowledge of a particular task domain that is widely shared
+ Heuristic Knowledge – more judgmental knowledge of performance in a task domain.

Uses of Expert Systems
– Very useful to companies with a high-level of experience and expertise that cannot easily be transferred to other members.
– Solves problems that would normally be tackled by a medical or other professional.
– Currently used in fields such as accounting, medicine, process control, financial service, production, and human resources

Prominent Expert Systems
> MYCIN – used to diagnose infectious blood diseases and recommend antibiotics.
> DENDRAL – embedded a chemist’s knowledge of mass spectrometry rules to use in analysis.
> CADUCEUS – used to analyze blood-borne infectious bacteria
> CLIPS and Prolog programming languages are both used in expert systems
– The Age of Empire game uses CLIPS to control its AI

Building an Expert System
+ Can be built from scratch – using lots of if-then-else statements.
+ There are many products being sold to make programming these systems easier.
A few that I’m aware of:
– Exsys – http://www.exsys.com – provides an easy to use user interface to develop traditional applications or web-based solutions.
– Barisoft – http://www.barisoft.com – developed by a PSU professor and finely tuned by his students
– CLIPS – provides a complete environment for the construction of rules and/or object based expert systems
– Jess – the Rule Engine, built

Components of an Expert System
> Set of Rules – derived from the knowledge base and used by the interpreter to evaluate the inputted data
> Knowledge Engineer – decides how to represent the experts knowledge and how to build the inference engine appropriately for the domain
> Interpreter – interprets the inputted data and draws a conclusion based on the users responses.

Problem-solving Models
+ Forward-chaining – starts from a set of conditions and moves towards some conclusion
+ Backward-chaining – starts with a list of goals and the works backwards to see if there is any data that will allow it to conclude any of these goals.
+ Both problem-solving methods are built into inference engines or inference procedures
Knowledge Objects
– Classes – questions the user is asked
– Parameters – place holder for a character string which can be variable and used to decide if/when a question is asked
– Procedures – definitions of calls to external procedures
– Rule Nodes – inferencing is done by a tree structure (decision trees!) and the nodes are called rule nodes.

Advantages of Expert Systems
+ Provide consistent answers for repetitive decisions, processes and tasks.
+ Hold and maintain significant levels of information.
+ Reduce employee training costs
+ Centralize the decision making process.
+ Create efficiencies and reduce the time needed to solve problems.
+  Combine multiple human expert intelligences
+ Reduce the amount of human errors.
+ Give strategic and comparative advantages creating entry barriers to competitors
+ Review transactions that human experts may overlook.

Disadvantages of Expert Systems
> Lack human common sense needed in some decision making.
> Will not be able to give the creative responses that human experts can give in unusual circumstances.
> Domain experts cannot always clearly explain their logic and reasoning.
> Challenges of automating complex processes.
> Lack of flexibility and ability to adapt to changing environments.
> Not being able to recognize when no answer is available.

References :
– “Expert Systems and Artificial Intelligence”. Engelmore, R., Feigenbaum, E., Chapter 1. http://www.wtec.org/loyola/kb/c1_s1.htm
– “The Origin of Rule-Based Systems in AI”, Davis, R., King, J.
– “Expert System – Wikipedia”, http://en.wikipedia.org/wiki/Expert_system

Facts, Rules, Predicates, and Variables in PROLOG

(1) Type the following program into a file and load it into Prolog.

/* Animals Database */
animal(mammal,tiger,carnivore,stripes).
animal(mammal,hyena,carnivore,ugly).
animal(mammal,lion,carnivore,mane).
animal(mammal,zebra,herbivore,stripes).
animal(bird,eagle,carnivore,large).
animal(bird,sparrow,scavenger,small).
animal(reptile,snake,carnivore,long).
animal(reptile,lizard,scavenger,small).

Devise and test goals to find (a) all the mammals, (b) all the carnivores that are mammals, (c) all the mammals with stripes, (d) whether there is a reptile that has a mane.

(2) Type the following program into a file

/* Dating Agency Database */
person(bill,male).
person(george,male).
person(alfred,male).
person(carol,female).
person(margaret,female).
person(jane,female).

Extend the program with a rule that defines a predicate couple with two arguments, the first being the name of a man and the second the name of a woman.
Load your revised program into Prolog and test it.

Okay, guys! This is our homework for this time. So, how can we find the answer? Now, this is the solution….
Question Number 1
1. Type all words in the box in Notepad, save it and don’t forget to insert .pl at the end of your name.

2. Consult your saved file in PROLOG.
3. To find the answer of number 1.a, you must type this.
?- animal(mammal,X,_,_).
Then press Enter.
4. To find another answers, type ; then another answers can appear until word No appears. It means there is no answer again.

5. To find the answer of number 1.b, you must type this.
?- animal(mammal,Y,carnivore,_).
Then press Enter.
6. To find another answer, follow the instruction number 4.

7. To find the answer of number 1.c, you must type this.
?- animal(mammal,Z,_,stripes).
Then press Enter.
8. To find another answer, follow the instruction number 4.

9. To find the answer of number 1.d, you must type this.
?- animal(reptile,R,_,mane).
Then press Enter.
10. The answer must be No, because there is no reptile has mane in that program.

Question Number 2

1. Type all words in the box in Notepad.
2. We must make a rule to find all possible couples. The couple must a man and a woman, not both of them are men or women. So the correct rule for this problem is :
couple(X,Y) :- person(X,male),person(Y,female).
3. Type it and save but don’t forget to insert .pl at the end of your name.

4. Consult your saved file in PROLOG.
5. To find the answer, type this
?- couple(X,Y).
Then press Enter.
4. To find another answers, type ; then another answers can appear until word No appears. It means there is no answer again.

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