QoS-based service composition enables the development of complex business applications. They are composed of distributed services characterized by QoS attributes representing non-functional characteristics, such as cost, execution time, and reliability. With the proliferation of services on the Internet, more candidates for each component service may be available with different QoS values. Hence, the ones satisfying QoS global constraints required for the application have to be selected. Automated negotiation is adopted to select component services in a dynamic market of services where provided QoS values may vary according to different market strategies. Nevertheless, when dealing with multiple QoS attributes, multiple service providers, and not shared information, it is difficult to guarantee the formal properties of the negotiation outcomes. In the present work, we propose a trade-off negotiation strategy that allows reaching a Pareto-optimal agreement, if it exists. The agreement consists of the QoS values of component services that are the ones selected to provide the complete application. The strategy exploits both the competition, that is due to multiple services providing the same functionality with different QoS values, and the cooperation among the providers of the different component services, that are necessary to meet the required end-to-end QoS constraints.

基于QoS的服务组合可以开发复杂的业务应用程序。它们由分布式服务组成，这些服务的QoS属性代表了非功能性特征，例如成本，执行时间和可靠性。随着Internet上服务的激增，具有不同QoS值的每个组件服务的更多候选者可能可用。因此，必须选择满足应用程序所需的QoS全局约束的那些。在服务动态市场中采用自动协商来选择组件服务，其中提供的QoS值可能会根据不同的市场策略而有所不同。但是，当处理多个QoS属性，多个服务提供者而不是共享信息时，很难保证协商结果的形式属性。在当前的工作中，我们提出了一种折衷的谈判策略，该协议可以达成帕累托最优协议（如果存在）。该协议由组件服务的QoS值组成，这些值是为提供完整应用程序而选择的。该策略利用了竞争（这是由于多个服务提供具有不同QoS值的相同功能）以及满足所需的端到端QoS约束所必需的不同组件服务的提供者之间的协作。