---
title: Mapping definition examples
slug: '66'
canonical_url: https://docs.coveo.com/en/66/
collection: index-content
source_format: adoc
---
# Mapping definition examples
A [mapping](https://docs.coveo.com/en/217/) definition has the following properties:

* A `content` array, where each string element (that is, each _rule_) must follow the [mapping rule syntax](https://docs.coveo.com/en/1839/).

> **Important**
>
> The `content` array elements of a mapping (its rules) are evaluated sequentially.
> 
> As soon as a rule yields a non-null value, the [Coveo indexing pipeline](https://docs.coveo.com/en/184/) uses this value to populate the target [field](https://docs.coveo.com/en/200/), and the sequential evaluation ends.
> 
> This implies that if the first rule of a mapping contains a hardcoded string (for example, `"My string"`), this rule will _always_ populate the target field, and none of the subsequent rules will be evaluated.

* The name of the target `field` that should be populated with the first non-null value yielded by a rule from the `content` array.
This field must exist in the target [Coveo organization](https://docs.coveo.com/en/185/) [index](https://docs.coveo.com/en/204/).
See [Create fields with the API](https://docs.coveo.com/en/144/) for details on field creation.

## Mapping a metadata to a field of the same name

This is the most basic kind of [mapping](https://docs.coveo.com/en/217/) you can define.

```json
{
  "content": [
    "%[product_name]"
  ],
  "field": "product_name"
}
```

> **Note**
>
> By default, the Coveo indexing pipeline automatically tries to use incoming Push [source](https://docs.coveo.com/en/246/) [item](https://docs.coveo.com/en/210/) [metadata](https://docs.coveo.com/en/218/) to populate the [field](https://docs.coveo.com/en/200/) whose name matches that of this metadata key.
> 
> This means that in a Push source, you never need to explicitly define mapping rules where the incoming metadata key and target field names are identical.
> 
> This also implies that each metadata you want this default mapping behavior to apply to in a Push source must have a field of the same name in the target [index](https://docs.coveo.com/en/204/).
> See [Create fields with the API](https://docs.coveo.com/en/144/) for details on field creation.
> 
> See [About Push Source Item Metadata](https://docs.coveo.com/en/115/).

## Mapping a metadata to a field with a different name

You may want to [map](https://docs.coveo.com/en/217/) [metadata](https://docs.coveo.com/en/218/) and [field](https://docs.coveo.com/en/200/) whose names differ.

A common use case for this is when your [index](https://docs.coveo.com/en/204/) contains a field whose name is prefixed for a certain [source](https://docs.coveo.com/en/246/), but whose purpose is identical to that of the corresponding un-prefixed standard field.
For example, the `mysource_date` field could serve the same purpose as the `date` field, but be specific to the `mysource` source.

```json
{
  "content": [
    "%[author]"
  ],
  "field": "mysource_author"
}
```

## Mapping a concatenated string to a field

The [mapping](https://docs.coveo.com/en/217/) rule syntax allows you to combine many [metadata](https://docs.coveo.com/en/218/) references and hardcoded strings into a single mapping rule.
When such a rule applies, its target [field](https://docs.coveo.com/en/200/) is populated by the resulting concatenated string.

```json
{
  "content": [
    "%[civic_number], %[street_name]"
  ],
  "field": "address"
}
```

## Defining several alternative mapping rules for a field

When a certain [mapping](https://docs.coveo.com/en/217/) includes more than one rule, those rules are evaluated sequentially.

In this example, the `rating` [field](https://docs.coveo.com/en/200/) may be populated by one of three distinct rules, depending on what [metadata](https://docs.coveo.com/en/218/) is available when an [item](https://docs.coveo.com/en/210/) passes through the [Coveo indexing pipeline](https://docs.coveo.com/en/184/):

* If the item has an `internal_rating` metadata value, this value populates the field.

* Otherwise, if the item has an `external_rating` metadata value, this value populates the field.

* Finally, if all else fails, the `"No rating"` hardcoded string populates the field.

```json
{
  "content": [
   "%[internal_rating]",
   "%[external_rating]",
   "No rating"
  ],
  "field": "rating"
}
```