4.3.4 Summary


Concepts are enclosed in square brackets and follow one of these general schemas:

[Type : Referent]
[Type = Descriptor]
[Type : Referent = Descriptor]


The type can be any identifier, and should generally be included in the type hierarchy to be most useful. The type can also be a variable, in which case the Prolog system must be able to infer the type.


Referents can be either:

  1. Identifiers,
  2. Strings
  3. Variables, or
  4. Multi-referents.

Multi-referents look like this: "*1", "*2", ..., "*9" and are used to say that a concept is really the same as another concept even though it is placed somewhere else textually. Multi-referents are different from coreference links. (We will get back to coreferents later).

Concept descriptors

Concept descriptors associate data with a concept. They can be any kind of Prolog+CG data, but the datatype most often used is conceptual graphs.


Next, we treat the problem of how to write graphs that extend over more than one textual line.

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