## Uses of #$genls and #$isa

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| Sets and Individuals in CYC®
| CYC® Predicates
| Mutually Disjoint Collections

Every CYC® constant is an element of at least one collection. In fact, everything that can appear in a CYC® expression is an element of some collection. Every collection, with the exception of #$Thing, is a subset of at least one other collection. These subset and instance of relations, expressed with assertions using #$genls and #$isa, make up the basic framework of the CYC® KB.

Heres a diagram showing some hypothetical constants and the #$genls and #$isa relations between them:

In this diagram, we introduce some conventions which will be used throughout the CYC® documentation:

- CYC® constants are represented as text in rectangular boxes.
- A constant with blue text denotes a collection.
- A constant with green text denotes an individual.
- Constants which could be either a collection or an individual are shown with black text.
- Assertions involving binary predicates are shown as lines between constants.
- #$isa assertions are shown as green lines.
- #$genls assertions are shown as blue lines.
- An abbreviation for the predicate in a binary assertion is placed near the middle of the line, using red text. A key to the abbreviations is included in the diagram.
- More general collections are placed higher on the page than their subsets.
- Collections are placed higher on the page than their instances.

The diagram therefore indicates the following assertions:

         (#$isa A #$Collection)
         (#$isa B #$Collection)
         (#$isa C #$Collection)
         (#$genls A #$Individual)
         (#$genls B #$Individual)
         (#$genls C B)
         (#$isa S C)
         (#$isa R A)
         (#$isa R B)

Last Update: 10/26/1998 11:41:21