# self

### Description

`self` is used to refer to the current [instance](/guides/glossary/instance.md) where you use it.

{% hint style="info" %}
This operator can only be used with [calculated information](broken://pages/-ML71u0p4UUNJ6GTeFl0).
{% endhint %}

### Example

```
CONCAT(self.last_name, ", ", self.first_name)
```

This [expression](/rule-language/expressions.md) calculates the full name of a person, by getting the information from the fields `first_name` and `first_name`.

If the expression is attached to an instance of the ‘Person’ [ontology](/guides/glossary/ontology.md), `self` tells the system to look for the field's first name within that instance.

If there is an Instance with the values for *Information Fields* `first_name` and `last_name` as Britta Johansdottir, this will return *'Johansdottir, Britta'.*


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