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Knowledge Representation using Frames in Artificial Intelligence

Knowledge Representation 
  • Frames are more structured form of packaging knowledge, - used for representing objects, concepts etc.
  • Frames are organized into hierarchies or network of frames.
  • Lower level frames can inherit information from upper level frames in network.
  • Nodes are connected using links viz.,
            → subc (links two class frames, one of which is subclass of other e.g., science_faculty class is ako of faculty class),
            → is_a (connects a particular instance of a class frame e.g., Renuka is_a science_faculty)
            → a_part_of (connects two class frames one of which is contained in other e.g., faculty class is_part_of department class).
           → Property link of semantic net is replaced by SLOT fields.
  • A frame may have any number of slots needed for describing object. e.g.,
           - faculty frame may have name, age, address, qualification etc as slot names.
  • Each frame includes two basic element : slots and facets.
          - Each slot may contain one or more facets (called fillers) which may take many forms such as :
                 ⇒value (value of the slot),
                 ⇒default (default value of the slot),
                 ⇒range (indicates the range of integer or enumerated values, a slot can have),
                ⇒demons (procedural attachments such as if_needed, if_deleted, if_added etc.) and
                ⇒other (may contain rules, other frames, semantic net or any type of other information). 


Frame Network - Example



Detailed Representation of Frame Network



Description of Frames
  • Each frame represent either a class or an instance.
  • Class frame represents a general concept whereas instance frame represents a specific occurrence of the class instance.
  • Class frame generally have default values which can be redefined at lower levels.
  • If class frame has actual value facet then decedent frames can not modify that value.
  • Value remains unchanged for subclasses and instances.
Inheritance in Frames
  • Suppose we want to know nationality or phone of an instance-frame13.
  • These information are not given in this frame.
  • Search will start from frame13 in upward direction till we get our answer or have reached root frame.
  • The  frame can be easily represented in prolog by choosing predicate name as frame with two arguments.
  • First argument is the name of the frame and second argument is a list of slot - facet pair.
Features of Frame Representations
  • Frames can support values more naturally than semantic nets (e.g. the value 25)
  • Frames can be easily implemented using object-oriented programming techniques.
  • Demons allow for arbitrary functions to be embedded in a representation.
  • But a price is paid in terms of efficiency, generality, and modularity !
  • Inheritance can be easily controlled.
Frames Examples :-

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