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Recent years have seen unprecedented growth in the popularity of social network systems, with Face-book being an archetypical example. The access control paradigm behind the privacy preservation mechanism of Facebook is distinctly different from such existing access control paradigms as Discretionary Access Control, Role-Based Access Control, Capability(More)
Access control policy is typically defined in terms of attributes, but in many applications it is more natural to define permissions in terms of relationships that resources, systems, and contexts may enjoy. The paradigm of relationship-based access control has been proposed to address this issue, and modal logic has been used as a technical foundation. We(More)
Social Network Systems pioneer a paradigm of access control that is distinct from traditional approaches to access control. Gates coined the term Relationship-Based Access Control (ReBAC) to refer to this paradigm. ReBAC is characterized by the explicit tracking of interpersonal relationships between users, and the expression of access control policies in(More)
Software execution environments like operating systems, mobile code platforms and scriptable applications must protect themselves against potential damages caused by malicious code. Monitoring the execution history of the latter provides an effective means for controlling the access pattern of system services. Several authors have recently proposed(More)
The Relationship-Based Access Control (ReBAC) model was recently proposed as a general-purpose access control model. It supports the natural expression of parameterized roles, the composition of policies, and the delegation of trust. Fong proposed a policy language that is based on Modal Logic for expressing and composing ReBAC policies. A natural question(More)
Inspired by the access control models of social network systems, Relationship-Based Access Control (ReBAC) was recently proposed as a general-purpose access control paradigm for application domains in which authorization must take into account the relationship between the access requestor and the resource owner. The healthcare domain is envisioned to be an(More)
We define a semantic model for <i>purpose</i>, based on which purpose-based privacy policies can be meaningfully expressed and enforced in a business system. The model is based on the intuition that the purpose of an action is determined by its situation among other inter-related actions. Actions and their relationships can be modeled in the form of an(More)
We hypothesize that, in a Facebook-style social network system, proper visualization of one's extended neighborhood could help the user understand the privacy implications of her access control policies. However, an unrestricted view of one's extended neighborhood may compromise the privacy of others. To address this dilemma, we propose a privacy-enhanced(More)
A workflow authorization model is defined in the framework of Relationship-Based Access Control (ReBAC), in which the protection state is a social network. Armed with this model, we study a new decision problem called workflow feasibility. The goal is to ensure that the space of protection states contains at least one member in which the workflow(More)
Users of an online community are willing to share resources because they can expect reasonable behaviour from other members of the community. Such expectations are known as social contracts. In this work, we study the specification and enforcement of social contracts in a computer mediated collaboration environment. Specifically, we examine social contracts(More)