# Define input data using an ID namespace
<a name="id-namespace"></a>

An *ID namespace* is a wrapper around your input data table. You use an ID namespace to provide metadata explaining your input data and matching techniques and how to use them in an [ID mapping workflow](create-id-mapping-workflow.md).

There are two types of ID namespaces: **Source** and **Target**.
+ The **Source** contains configurations for the source data that AWS Entity Resolution processes in an ID mapping workflow.
+ The **Target** contains a configuration of the target data that all sources resolve to.

You can define the input data that you want to resolve across two AWS accounts in an ID mapping workflow. One participant creates an ID namespace source and another participant creates an ID namespace target. After the participants create the source and target, you can run an ID mapping workflow to translate the data from the source to the target.

The following diagram summarizes how to create an ID namespace to use in an ID mapping workflow.

![A summary of the four steps to create an ID namespace in AWS Entity Resolution](http://docs.aws.amazon.com/entityresolution/latest/userguide/images/HIW-ID-Namespace.png)

The following sections describe how to create an ID namespace source and an ID namespace target. 

**Topics**
+ [ID namespace source](create-id-namespace-source.md)
+ [ID namespace target](create-id-namespace-target.md)
+ [Editing an ID namespace](edit-id-namespaces.md)
+ [Deleting an ID namespace](delete-id-namespace.md)
+ [Adding or updating a resource policy for an ID namespace](add-update-resource-policy-id-namespace.md)