NDL is a language I wrote in June 2008 that uses simple algegraic expressions to describe network objects. NDL defines everything in terms of objects, ports, and attributes. Any network element can be considered an object. Objects have ports. Objects and ports have attributes. Bigger objects are made by adding together smaller objects using algegra. When that happens, the bigger object inherits the ports and attributes of the smaller objects, as determined by the algebra.

A tutorial and language reference is contained in the NDL 1.0 whitepaper.
A basic overview is contained in the NDL 1.0 presentation.
Here is a link to the Communications Technology Magazine article on NDL in their Aug 2008 issue.

PS: There are lots of acryonym collisions. Here is a list of other NDL acronyms.