XMLMAP Files: Shared XML Maps
Files with the extension XMLMAP contain, as you might expect, XML maps. You can use XML maps when your service must handle a particular format for XML messages it receives or send a particular format to other components. XML maps your service uses can be kept inline with the code for your service or stored in a separate map file with an XMLMAP extension.
When you keep XML maps in a map file, you get the added benefit of being able to use the maps from various places in your code; inline maps, on the other hand, may be applied only to the code they precede.
For step-by-step instructions on creating an XML map file, see How Do I: Begin a Reusable XML Map?