# 11 Nested graphs

## Definition

When a conceptual graph G1 is nested inside a concept C, it means that:
• either G1 is directly part of the referent of C,
• or G1 is directly part of the referent of a concept C2 which is nested inside C.

## This is a recursive definition

Note that this is a recursive definition. We define the notion "nested" first in terms of a base case: "directly part of the referent of C", and then in terms of a recursive case: "part of the referent of a concept which is nested inside C".

## Example

An example of a conceptual graph nested in another conceptual graph could be:

```   [Proposition: [Professor: Alfred]->(Attr)->[Good] ]
"There is a proposition, which is
'Alfred is a good professor'"
```

Here, the sub-graph

```   [Professor: Alfred]->(Attr)->[Good]
```

is nested within the concept with concept type 'Proposition'.

## Next

Two concepts are key when talking about nested graphs. One is the concept of context, while the other is the concept of nesting. In the following, we discuss contexts first and then nesting.

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