Methods for service specification should be simple and intuitive. At the same time they should be precise and allow early validation and detection of inconsistencies. UML 2.0 collaborations enable a systematic and structured way to provide overview of distributed services, and decompose cross-cutting service behaviour into features and interfaces by means of collaboration-uses. To fully take advantage of the possibilities thus opened, a way to compose (i.e. choreograph) the joint collaboration behaviour is needed. So-called collaboration goal sequences have been introduced for this purpose. They describe the behavioural composition of collaboration-uses (modeling interface behaviour and features) within a composite collaboration. In this paper we propose a formal semantics for collaboration goal sequences by means of hierarchical coloured Petri-nets (HCPNs). We then show how tools available for HCPNs can be used to automatically analyse goal sequences in order to detect implied scenarios.