We introduce the main elements of UML extension to support QoS specifications, which are the basic constructors of QoS-aware models. Different types of languages are used to specify QoS systems, the most common include extensions of Interface Description Languages, UML extensions and metamodels, and mathematical models. QoS specification methods support the description of QoS concepts that are used for different purposes: i) generation of code for the management of QoS concepts (e.g., negotiation, access to resource managers), ii) specification of QoS-aware architectures, and iii) management of QoS information in QoS reflective infrastructures (e.g., QoS adaptable systems).

QoS-aware models support the description of software architectures with quality requirements. The extensions included in this paper are part of an initial submission of OMG RFP "UML Profile for Quality of Service and Fault Tolerance Characteristics and Mechanisms".