SLIDE 1
2
Basics
Conceptual graph (john Sowa 1984) is an
example of network representation language
A CG is a finite, connected, biparte graph Nodes are concepts or conceptual relations No labeled arcs, conceptual relation nodes
Conceptual Graphs KR Chowdhary, Professor Department of Computer - - PowerPoint PPT Presentation
Conceptual Graphs KR Chowdhary, Professor Department of Computer - - PowerPoint PPT Presentation
Conceptual Graphs KR Chowdhary, Professor Department of Computer Science & Engineering, MBM Engineering College, JNV University, Jodhpur, Basics Conceptual graph (john Sowa 1984) is an example of network representation language A
SLIDE 2
SLIDE 3
3
Simple examples
bird dog child flies colour brown Flies is a 1-ary Relation. Colour is a 2-ary Relation. parents mother father Parents is a 3-ary relation
SLIDE 4
4
Basics
Concept objects are concrete (those form an
image, like – telephone, chair, etc.) or abstract (like – affection, hate, scold, appreciate, etc)
Relation can be of any arity, in general arity
n.
Each conceptual graph represents single
proposition, and a knowledge base will consist number of such graphs
SLIDE 5
5
Examples
Person:mary agent book give Person:john
- bject
recipient CG for “Mary gave john the book.”
SLIDE 6
6
Representation
CG allow us to represent specific but
unnamed objects
A unique token is #
dog: # 1234
- Generic marker * is used to indicate an unspecified
- Individual. Thus, a node given by label dog is
Equivalent to dog:* .
- Named variables are represented by * varname.
SLIDE 7
7
Examples:
dog:* X paw ear scratch dog:* X part instrument part
- bject
agent CG for the sentence “The dog scratches its ear with Its paw.”
SLIDE 8
8
Generalization and specialization
The theory of CG includes a number of operations
that create new graphs from existing graphs.
These allow for the generation of new graph by
either specializing or generalizing an existing graph. This is important for representation of semantics of NL.
Four operations: copy, restrict, join, and simplify
perform these jobs.
SLIDE 9
9
Copy and restrict
Copy rule allows to form a new graph which is exact
copy of previous.
Restriction allows concepts nodes in a graph be
replaced by a node representing their specialization. These cases are:
- 1. If concept is labeled by generic marker, it may be
replaced by an individual marker
- 2. A type label may be replaced by one of its
subtypes.
SLIDE 10
10
Restrict and join
One use of restriction rule is to match two concepts
so that a join can be performed
Join and restriction allow the implementation of
- inheritance. Steps are:
- 1. Replacing generic marker by individual inherits the
properties of the type by individual
- 2. Replacing type label by subtype defines inheritance
between class and superclass.
SLIDE 11
11
Restriction
brown bone eat dog colour
- bject
agent brown porch Animal:”emma” location color g1: g2:
SLIDE 12
12
Restriction..
brown porch dog:”emma” location color g3: Result: The restriction of g2. Note: g2 is generalization of g3.
SLIDE 13
13
Join
porch bone eat dog:”emma” location
- bject
agent colour colour porch g4: Join of g1 and g3. Note: Join is a specialization rule.
SLIDE 14
14
Simplify
porch bone eat dog:”emma” location
- bject
agent colour porch g5: Simplify of g4.
SLIDE 15
15
Uses of CGs:
Natural language understanding Commonsense reasoning Individual sentences CGs can be joined