Trust Management of Dynamic Virtual Organisations in XtreemOS

The notion of Virtual Oranisations (VOs) is widely used in computational Grids to manage large numbers of users and computing nodes. A VO is defined as a set of users and real organisations that provide resources they want to exploit for a common goal. In Grid computing, physical machines, services, applications, and data sets can all be seen as resources. Dynamic VOs are created on-demand in response to requests from users. They tend to be short-lived and are characterised by the possibility of users and resources joining and leaving during their lifecycle. The underlying environment for the creation of dynamic VOs consists of a large number of resource providers, which have interests in pursuing common future goals and share compatible infrastructures and technologies. Such environments are usually termed virtual breeding environments [?], out of which VOs emerge. In such environments, resource access and usage across multiple administrative domains becomes challenging given the dynamic nature of VOs. Even the most basic authentication and identity management are no trivial tasks. This paper describes the management of dynamic VOs, and the underlying trust model, when using the XtreemOS Grid-based operating system. 1.1 A Virtual Market Place of e-Learning Resources In order to illustrate the requirements of a dynamic VO, consider the following use case scenario taken from the e-Learning domain [?]. The main actors are: End Users–learners who wish to acquire or complement their skills in