If you can't enforce it, contract it: Enforceability in Policy-Driven (Linked) Data Markets

The Web of Data refers to a network of data, which is published from various data sources, distributed across different machines, and possibly interconnected as Linked (Open) Data. We assume that in the near future these machines will not only publish and consume data, but will also perform transactions in digital data markets without human intervention. For these digital data markets to succeed, it is crucial that published data is accessed and used in a manner, which is compliant with restrictions or regulations that have been defined by data publishers. While it is fairly simple to express access policies using one of the numerous vocabularies available, the actual enforcement of those policies is rather difficult especially when taking dependencies among policies into account. In this paper, we demonstrate how ODRL can be used not only to represent access policies but also to specify access requests, offers and agreements, and propose an approach to generate on-the-fly contracts that govern all explicit and implicit non-enforceable policies.