# Mapping Input Specification
The **Mapping Input Specification** step is an input placeholder used inside a mapping *sub-transformation*.
Use this step to define where the sub-transformation expects input rows from the parent transformation.
You can think of it as a special input step that receives data from the parent transformation at runtime.
### When to use
Use **Mapping Input Specification** when your transformation is designed to be executed as a mapping (for example, from the [Mapping](/pdia-data-integration/pdi-transformation-steps-reference-overview/mapping.md) step or the [Simple Mapping (sub-transformation)](/pdia-data-integration/pdi-transformation-steps-reference-overview/simple-mapping-sub-transformation.md) step).
A sub-transformation can contain:
* One Mapping Input Specification step (common)
* Multiple Mapping Input Specification steps (multiple entry points)
* No Mapping Input Specification steps (no input)
### Options
| Option | Description |
| ----------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Step name** | Name of the step. This name must be unique within the transformation. |
| **Name** | Field name as it is used inside the sub-transformation. |
| **Type** | Data type of the field. |
| **Length** | Maximum string length. |
| **Precision** | Maximum number of decimals. |
| **Include unspecified fields, ordered by name** | In some cases, you may want all incoming fields, not only the required fields. For example, you might remove certain fields later while retaining all others.
During design time, unspecified fields are not available in field picklists because they are available only at runtime.
|
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