Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Lecture 6 Knowledge Representation Non-Formal Method Semantic Nets Frames

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Semantic Nets A semantic network focuses on the graphical representation of relations between elements in a domain. Components are nodes and links Nodes: used to represent domain elements (normally represented with rectangles and in some books with ellipse) Links (or arcs): represent the relationship between the elements. Shown as vector from one element to the other element

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Examples Hassan eats meat Nodes: hassan and meat Link: eating HassaneatsMeat Link can be viewed as something that asserts to be true about one element relative to another. An assertion can only be true or false, therefore fundamentally its BINAR RELATION (examples of binary relation ISA, PART OF etc.)

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Examples, cont.. Hassan isa mammal Nodes: hassan and mammal Link: isa Hassanisamammal Horse has a tail Tailpartof Horse

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Examples, cont.. Horse is a mammal with tail TAIL HORSEMAMMAL partof isa

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Examples, cont.. Instance: a specific example of a class is the instance of that class. Animals are a class of living beings. Humans are subclass of animals and Zahra is an instance of subclass human, class animals Horse is a mammal with a tail. Tony is horse of black color TAIL HORSE MAMMAL partof isa BLACKTONY color instance

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Examples, cont.. Property Inheritance: The properties of the class are inherited by the instances by default, unless specified.Tony in the example below also has a tail. TAIL HORSE MAMMAL partof isa BLACKTONY color instance

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Examples, cont.. Problem:Animals have types reptiles and mammals. All Mammals have heads. Element is a typical mammal with grey color and large size. A and b are two elephants. A likes bananas and and B eats oranges. Nodes: Animals, reptiles, mammals, elephants, A, B, bananas and oranges

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Examples, cont.. Problem:Animals have types reptiles and mammals. All Mammals have heads. Element is a typical mammal with grey color and large size. A and b are two elephants. A likes bananas and and B eats oranges. ANIMAL REPTILES MAMMALSHEAD ELEPHANT GREY LARGE B AORANGES BANANAS subclass eats has_part size color likes instance

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Examples, cont.. Problem: Vertebrates are animals with several types. Birds are type of vertebrates with feathers. Using these feathers they can fly. A bluebird is typical bird with blue colour and small size. Horses are also vertebrates, but are mammals. They have tails and cannot fly. Trigger is a horse with white colour. This horse is very old and is nearly dead.

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Examples, cont..

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Examples, cont.. Problem: Snow is form of water, it is soft, slippery and white in color. Ice is also formed of water and share all the properties of snow except that it is hard and clear. One can form snowman from ice frosty is a snow man that I saw in the forest.

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Frames Frames are a variant of semantic networks, and a popular way to represent facts in expert systems Relevant information is stored in single complex entity called frames Frames support inheritance, superficially similar to data structure (struct)

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Example Problem:Animals have types reptiles and mammals. All Mammals have heads. Element is a typical mammal with grey color and large size. A and b are two elephants. A likes bananas and and B eats oranges. Mammal: subclass: Animal has_part: head Elephant:: subclass: Mammal color:grey size:large A: instance:Elephant likes:bananas Reptiles: subclass: Animal objects Slot values

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Default and Multiple Inheritance Mammal: subclass: Animal has_part: head warm_blooded: yes  angry: yes Elephant:: subclass: Mammal has_trunk: yes  color:grey  size:large  angry:no A: instance:Elephant color:pink owner:Farid likes:bananas B:instance:Elephant size:small Mammal: subclass: Animal has_part: head warm_blooded: yes  angry: yes Elephant:: subclass: Mammal has_trunk: yes  color:grey  size:large  habitat:jungle Circus_Animal: subclass:Animal habitat:tent skills:balancing on a ball A: instance:Circus_Animal Elephant color:pink owner:Farid Default values are those values that can be overridden and changed for subclass and/or instances ? Multiple Inheritance: When more than one parent class is present, which attribute is to be passed.

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Implementing Simple Frames IF slot_value (O,P) returns a value V, return V. Otherwise, IF slot_value(O,subclass) or slot_value(O,instance) return C, find value(C,P ) and return this value Otherwise, fail O=object, P=Attribute/Property slot_value(O,subclass) checks whether O is a subclass or not slot_value(O,instance) checks whether O is a instance or not

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Example of the Algo. Question 1: What does elephant A likes? Step one: O = elephant A, P=likes Evaluate value(A,likes) returns bananas query successful

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Example of the Algo. Question 1: What is the color of the elephant A ? Step one: O = elephant A, P=color Evaluate value(A,color) returns nil query not successful Step Two Evaluate slot_value(A,subclass) returns nil A s not subclass Evaluate slot_value(A,instance) returns Elephant Evaluate slot_value(Elephant, colour) returns grey

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Example DEVELOP A FRAME FOR A CAR

Lahore University of Management Sciences, Lahore, Pakistan Dr. M.M. Awais- Computer Science Department Example: CAR FRAME