Expressing Cloud Security Requirements in Deontic Contract Languages

The uptake of Cloud computing is being hindered by the fact that not only are current Cloud SLAs written
in natural language, but they also fail to cover security requirements. This paper considers a Cloud brokering
model that helps negotiate and establish SLAs between customers and providers. This broker handles security
requirements on two different levels; between the customer and the broker, where the requirements are stated
in natural language; and between the broker and the different Cloud providers, where requirements are stated
in deontic contract languages. We investigate the suitability of seven of those languages for expressing security
requirements in SLAs and exemplify their use in the Cloud brokering model through a practical use case for a
video streaming service.