# 10 Coreferents

## Definition

Two or more concepts in a conceptual graph may refer to the same individual. This is shown by a dotted line. The dotted line is called a "coreference link".

## Examples

E.g.:

```   [Person: #you]- - - -[Person: Peter]
"There is a person, you, and a person, Peter, and these two
concepts are coreferential (i.e., are the same)."
"You are Peter."
```

Another example:

```   [Person: Socrates]- - -[Man]->(Attr)->[Mortal]
"There is a Man who has an attribute which is mortal.  This man is
the same as the person Socrates"
"Socrates is a mortal man"
```

In the graphical notation, the first example would look like this:

```
"Tu es Petrus"
```

## When we can't draw dotted lines in the linear notation

If the two concepts are not located next to each other, it is not easy to draw dotted lines in the linear notation. There is a solution, however. For example, the following graph:

```
"There is a situation which can be described as follows.  There is
a Rhino, Otto, which has a characteristic, which is a Color which
is Orange.  And there is a Rhino in the living room.  Otto is that
rhino."

"There is the following situation: Otto the orange rhino is in the
living room."
```

could look like this in linear notation:

```   [Situation:

[Rhino: Otto *x]->(Chrc)->[Color: Orange]

[Rhino: ?x]->(In)->[Room: LivingRoom]

]
"There is this situation: There is a Rhino, Otto, and let us call
this Rhino 'x'.  Otto has the color orange.  'x' is in the living
room."
```

## Unconnected graphs are related by 'and'

Note how we have two conceptual graphs nested in the Situation concept. Note also these two subgraphs are not connected:

```     [Rhino: Otto *x]->(Chrc)->[Color: Orange]
```

and

```     [Rhino: ?x]->(In)->[Room: LivingRoom]
```

When two graphs are not connected, the relationship between them is interpreted as "and". In the above example, it is both true that Otto the rhino is orange and that Otto is in the living room.

## Defining label, bound label

The label '*x' is called the defining label, while the label '?x' is called the bound label. We could use '?x' more than once in the same context to refer to the concept '*x'. However, we could only have one '*x' in the same context.

This is because '*x' is used as the "anchor point" for the definition of the coreferent, while all the '?x's "bind to" the single instance of '*x'. Hence the names defining label and bound label.

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