Sharif Digital Repository

With the growth of semantic-aware environments, such as semantic web, new security requirements are imposed in access control procedures. An access control model for semantic web should take the semantic relationships (in three scopes of subject, object and action) into account in its access decisions. Considering the advantages of logic based models and description logic foundation of semantic web, we use the description logic as a basis to propose access control models in this environment. On the other hand, in some applications, such as e-banking environments, policy definition with the constraint(s) based on previous users’ accesses might be crucial. To consider this aspect, in this... 

Description logic is a family of knowledge representive languages which represents knowledge via propositional logic (first order logic) propositions and constructors and applies its services for reasoning and consistency checking. Nowadays description logic and its popular reasoner FaCT++ which applies tablue reasoning technique are widely used in applications such as semantic web and onthologies. Model checking is a technique for systems and models verification and to guarantee the accuracy of design. Given a model description and a specification formula, the model checker verifies the model against the specification and decides if the model satisfies the description or not. Main model... 

Growth of tools that ease sharing information and resources in social networks can cause privacy issues for the users. Protecting user’s personal information against unauthorized access is a crucial task, and it is considered as a first step for preserving user’s privacy in such networks. Policies, access control rules, and the way rules are applied to online social networks are issues that are less investigated and most existing frameworks have used simple models. Growth of users joining social networks and significant volume of resources shared in these networks make such environments suitable for using semantic technology. Semantic technology is used for modeling various resources, users,... 

Semantic technology provides an abstraction layer above existing computational environments, especially the Web, to give information a well-defined meaning. Moving toward semantic-aware environments imposes new security requirements. One of the most important requirement is the authorization and security policy inference based on the existing semantic relationships in the abstract (conceptual) layer. Most of the authorization models proposed for these environments so far are incomplete and their inference rules are not guaranteed to be consistent, sound, and complete. To have a sound and complete system for policy specification and inference, in this thesis, a family of modal logics, called...