Summary: We extend the service abstraction in the Open Grid Services Architecture for Quality of Service (QoS) properties [{\it I.~Foster, C.~ Kesselman, J.~F. Nick} and {\it S. Tuecke}, “The physiology of the grid: an open grid services architecture for distributed systems integration" (2002), downloadable at: http://www.globus.org/research/papers/ogsa.pdf]. The realization of QoS often requires mechanisms such as advance or on-demand reservation of sources, varying in type and implementation, and independently controlled and monitored. Foster et al. proposed the GARA architecture [{\it I.~Foster, C.~Kesselman, C.~Lee, B. Lindell, K.~Nahrstedt} and {\it A.~Roy}, “A distributed resource management architecture that supports advance reservation and co-allocation", in: Proceedings of the International Workshop on QoS, 27‒36 (1999)]. The GARA library provides a restricted representation scheme for encoding resource properties and the associated monitoring of Service Level Agreements (SLAs). Our focus is on the application layer, whereby a given service may indicate the QoS properties it can offer, or where a service may search for other services based on particular QoS properties.