Descartes Modeling Language is an architectural modeling language that enables designers to build models that can be used to do performance predictions and system adaptations at runtime. Its distinctive characteristic when compared to Palladio Component Model (PCM) is that it is mainly intended to be used at runtime to enable self-adaptation (not at design time as PCM).
The central idea is summarized here: "DML is designed to serve as a basis for self-aware resource management1 [1, 2] during operation ensuring that system quality-of-service requirements are continuously satisfied while infrastructure resources are utilized as efficiently as possible."
I guess that a good start point is this "tutorial": http://opus.bibliothek.uni-wuerzburg.de/files/10488/DML-TechReport-1.0.pdf
Best regards,
Fábio