Abstract. Service-oriented computing has become the de-facto way of developing distributed applications and, in such systems, an accurate assessment of reputation is essential for selecting between alternative providers. Existing methods typically assess reputation on a combination of direct experiences by the client being provided with a service and third party recommendations, but they exclude from consideration a wealth of information about the context of providers' previous actions. Such information is particularly important in composite service provision scenarios, where providers may delegate sub-tasks to others, and thus their success or failure needs to be interpreted in this context and reputation assessed according to responsibility. In response, to enable richer, more accurate reputation mechanisms, this paper models the delegation knowledge underlying a composite service provision, and incorporates such knowledge into the reputation assessment process, adjusting the contributions of past interactions with the composite service provider according to delegation context relevance. Experimental results demonstrate the effectiveness of the proposed approach.