Using SLA Context to Ensure Quality of Service for Composite Services

As service-orientation is establishing itself as the dominant design and integration paradigm for large heterogeneous and open systems, the lines between wired and wireless consumers and providers begin to blur. Due to the availability of toolkits and standards it is now fairly easy to build nomadic service consumers that provide users transparent access to enterprise services. However, since nomadic consumers are typically characterized by limited computational resources, they are very dependent on reliable service providers. Unlike their more resource rich wired counterparts, that can in case of a provider slowdown or failure simply rebind to an alternative provider, the nomadic consumers lack the bandwidth to execute to do so in sufficient time. This leads to the question of how to ensure QoS for providers of nomadic consumers. Especially for composite services that aggregate other services this is still an open question. This paper presents an approach for ensuring QoS for nomadic applications that consume composite services. Using transparent proxies that are control the access to each service provider the scheduling of requests and therefore the enforcement of QoS becomes possible.