01-01-2013, 03:16 PM
Knowledge Representation using structured objects
Knowledgerepresentation.ppt (Size: 121.5 KB / Downloads: 117)
Semantic nets
knowledge is represented as a collection of concepts, represented by nodes (shown as boxes in the diagram), connected together by relationships, represented by arcs (shown as arrows in the diagram).
certain arcs - particularly isa arcs - allow inheritance of properties.
Developments of the semantic nets idea:
psychological research into whether human memory really was organised in this way.
used in the knowledge bases in certain expert systems: e.g. PROSPECTOR.
special-purpose languages have been written to express knowledge in semantic nets.
How frames are organised
A frame system is a hierarchy of frames
Each frame has:
a name.
slots: these are the properties of the entity that has the name, and they have values. A particular value may be:
a default value
an inherited value from a higher frame
a procedure, called a daemon, to find a value
a specific value, which might represent an exception.
Frames: some examples
The following is an exploration of Minsky's frames, using simple examples.
Note that this is not exactly the way Minsky described frames in his original paper, but it is the way the idea has come to be used in practice.