7.4.1 Introduction

Introduction by means of an example

An example of a lambda expression could be:

   [Person: ?x]<-(Agnt)<-[Sing]
   "A person, x, is singing"

The symbol '?x' is a placeholder for something else that must come from outside of the lambda expression. This lambda expression could be used to define the concept "SingingPerson". For example, the following two would be equivalent:

   [SingingPerson: John]

and

   [ [Person: ?x]<-(Agnt)<-[Sing] : John ]

Notice how we can replace the concept type "SingingPerson" with the lambda expression and get exactly the same meaning.

The two main usages of lambda expressions

Lambda expressions are used in two situations:

  1. When defining new concept types, and
  2. When defining new relation types.

Since lambda expressions are the chief method of defining new concept types and new relation types in knowledge bases based on conceptual graphs, they are quite important. Next, we give some definitions.


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