A Deployment Descriptor file is an XML text file that identifies one or more Decision Services to be deployed, and the properties to be set on each Decision Service.

You can them with the Corticon management command line utility, or create them in a text editor.

Open a .cdd file in a text editor to see how it is formatted. The TradeAllocation.cdd sample located at a server installation's [WORK_DIR]\Samples\Rule Projects\Trade Allocation is a good example.