DDL allows a machine parseableparsable description of the interface and capabilities of any device to be defined.<ref name="EngArts">http://engarts.com/ddl/index.html</ref> This description can be interpreted by a controller which may then automatically configure itself for controlling that device. The description not only provides the address and property mapping information which is necessary for DMP to operate but it can also contain a huge amount of information on the functionality, capabilities and semantics of the device in an extensible format which allows a controller to extract the features it needs for its specific context while skipping over information which is not relevant to its needs.<ref>http://powers.media.mit.edu/wiki/upload/E1-17ACN2006DDL.pdf</ref>
DDL is an [[XML]] based language and descriptions are contained in a small number of [[XML]] documents. In normal ACN systems the description for a device may be downloaded from the device itelf. However, descriptions may also be distributed in other ways (such as internet download) and since a description is valid for all devices of the same type, controllers can typically maintain a cache of descriptions for devices they commonly encounter.
