In this paper we extend our previous work on soft probabilistic contracts for QoS management, from the particular case of "response time'', to general QoS parameters. Our study covers composite QoS parameters dealing not only with time aspects but also with Quality of Data. We also study contract composition (how to derive QoS contracts for an orchestration from the QoS contracts with its called services), and contract monitoring. Our approach supports comprehensive and flexible QoS management within a probabilistic framework.