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# $prop

## Concept:

$prop transforms a statement into a 'black box' proposition. This prevents Aito
from analyzing the proposition and using its parts separately in the statistical
reasoning.

In practice the difference between normal 'white box' expressions, and the $prop's
black box expressions is: that the atomic expressions have a smaller bias, but
a higher measurement error.

Consider the following example:

```
{ "tags" : "pen", "price" : { "$gte" : 200 } }
```

During the statistical reasoning: Aito may recognize that pens are often sold,
and that over 200€ product purchases are somewhat common. As a result: Aito might
assume the over 200€ pen to be a popular product.

Now, consider the expression:

```
{ "$prop" : { "tags" : "pen", "price" : { "$gte" : 200 } } }
```

The results of this expression will depend of the amount of data. If there are no
over 200€ pens in the data: Aito will make no assumptions of the proposition's effect.
On the other hand, if you have the data: Aito will recognize correctly, that the over 200€
pens are bought extremely rarely, and almost solely by corporations and wealthy individuals.

## Format:

```
{ "$prop" : Proposition }
```

## See also: