# Noun Phrases

## Overview

A **noun phrase** is a group of words centered around a noun. It consists of:

* **Head:** The main noun representing the fact.
* **Modifiers:** Optional words providing additional context to the head noun.

The `NounPhase` class can be used to represent a noun phrase.

## Modifiers

A **modifier** is an optional part of a noun phrase that provides additional detail about the **head** noun. It appears before the head and refines the fact being referenced.

#### Example: Creating a Noun Phrase with Modifiers

```python
# Create a noun phrase with a head and modifiers
np = NounPhrase("dog", ["big", "white"])
print(np)  # Outputs: big white dog
```

In this example:

* **Head:** "dog"
* **Modifiers:** "big", "white"

The resulting noun phrase is "big white dog".

***

## Parameters as Noun Phrases

Parameters can be defined as `NounPhrase` types to tell the system to use a fact's **name** instead of its **value**.

### Example: Defining a Parameter as a Noun Phrase

Consider the following procedure method definition, where the `city` parameter is defined as a `NounPhrase`:

```python
@procedure("to get the (current temperature) at a city")
def current_temperature(
  self, city: NounPhrase, unit: Optional[NounPhrase] = NounPhrase("metric")
) -> float:
```

This procedure can be called in an automation where **London** is a fact with a specific value:

```
London is "windy"
get the current temperature at London
```

In this example, when **London** is specified as the city parameter, the system uses the name of the fact (London) instead of its value ("windy").