  Collaboration models and tools aim at improving the efficiency and
effectiveness of human interactions. Although social relations among
collaborators have been identified as having a strong influence on
collaboration, they are still insufficiently taken into account in current
collaboration models and tools. In this paper, the concept of service protocols
is proposed as a model for human interactions supporting social requirements,
i.e., sets of constraints on the relations among interacting humans. Service
protocols have been proposed as an answer to the need for models for human
interactions in which not only the potential sequences of activities are
specified-as in process models-but also the constraints on the relations among
collaborators. Service protocols are based on two main ideas: first, service
protocols are rooted in the service-oriented architecture (SOA): each service
protocol contains a service-oriented summary which provides a representation of
the activities of an associated process model in SOA terms. Second, a
class-based graph-referred to as a service network schema-restricts the set of
potential service elements that may participate in the service protocol by
defining constraints on nodes and constraints on arcs, i.e., social
requirements. Another major contribution to the modelling of human interactions
is a unified approach organized around the concept of service, understood in a
broad sense with services being not only Web services, but also provided by
humans.
