Adaptive QoS systems are attractive for multimedia services that are accessed via the Internet or mobile computers. An important feature of an adaptive QoS system is that it allows application programs to specify the QoS level desired, and at the system to set the level according to the resources available. With an adaptive QoS system, the user should specify not only the target QoS, but also a QoS range to minimize the quality degradation resulting from resource shortages.This paper introduces QoSPath as an extensible object model for specifying, translating, and arbitrating QoS in adaptive QoS systems. The QoSPath model herein lets users and application programs specify their QoS preference by setting QoSPoints in a QoSPath, each of which specifies an objective QoS level against a subjective utility value.With the QoSPath model, a simple QoS preference can be specified by a few parameters, while more detailed specifications can be given by providing more information, thus the model offers both the simple and descriptive QoS specifications. It is designed to be flexible in that new QoS formats and translation modules can be easily defined with only a minimum knowledge of other parts of a system. It therefore separates the functions of QoS specification, translation/inverse-translation and arbitration.