Amazon SWF Domains
Domains provide a way of scoping Amazon SWF resources within your AWS account. All the components of a workflow, such as the workflow type and activity types, must be specified to be in a domain. It is possible to have more than one workflow in a domain; however, workflows in different domains cannot interact with each other.
When setting up a new workflow, before you set up any of the other workflow components you need to register a domain if you have not already done so.
When you register a domain, you specify a workflow history retention period. This period is the length of time that Amazon SWF will continue to retain information about the workflow execution after the workflow execution is complete.