One of the more confusing subjects covered in the Reference Architecture is execution context.
The document states: "the execution context of a service interaction is the set of infrastructure elements, process entities, policy assertions and agreements that are identified as part of an instantiated service interaction, and thus forms a path between those with needs and those with capabilities". It continues with: "an execution context often evolves during a service interaction. The set of infrastructure elements, the policies and agreements that apply to the interaction, may well change during a given service interaction".
The providers, consumers and any third parties must agree to a set of contractual agreements or commitments in order to initiate a service interaction, in effect 'buying into' the real world effects. This is the public part of the SOA process.
However, as the Reference Architecure notes, "it is simply not possible to specify, completely and unambiguously, the precise semantics of and all related information about a service. There will always be unstated assumptions made by the describer of a service that must be implicitly shared by readers of the description".
It is assumed that whatever is required will be described with "sufficient scope and precision to support intended use". One might hope so.