  In this paper, we present the design process of a novel solution for enabling
the collaboration between OpenStack cloud systems in SAML federations with
standalone attribute authorities, such as national research and education
federations or eduGAIN. The software solution that realizes the integration of
systems serves as a case study to show how abstract desirable engineering
properties fixed at the beginning of the design process can be implemented
during the development phase. An analysis of earlier generations of
OpenStack-related developments trying to tackle the same problem is given. Many
aspects of this software integration can be generalized to serve as a template
for federative cloud access.
