# HEAD Access Control Metamodel: Distinct Design, Advanced Features, and New Opportunities
## 1 Introduction
It is generic and able to include all features of common models (and any other model), dynamic and able to create the needed components/attributes to express a larger set of static and dynamic AC rules, extensible since the already defined models can be extended, and it supports the feature of hierarchy for any component. In addition to all the above, the emergence of COVID-19 as a global pandemic has had a huge impact on business and work strategies; moreover, it put the spotlight on access control. It forced a greater requirement than ever for access control, due to widespread telework and the need to access resources and data related to critical domains such as government, healthcare, industry, and others. As stated in Security Distributing and Marketing (SDM) magazine [10], \"The importance of controlling who has access to specific areas of a facility and the knowledge of who actually accessed specific areas became much more important\" due to the pandemic. All the aforementioned issues force the need to implement more robust, coherent, and advanced AC models, which are flexible, dynamic, and able to meet the AC requirementsand follow technology upgrades. In this paper, we present the new opportunities and the various research directions which would enhance our HEAD AC metamodel to meet the expected AC requirements with the presence of various technology trends. The characteristics of the HEAD metamodel open various research directions in the domain, for example, its unifying structure would facilitate developing many other essential features (e.g., collaboration and interoperability between various models and migration of AC policies), developing the necessary tools for policy analysis and assessment, integrating artificial intelligence techniques to support the necessary intelligent services with the current era of technologies, and many other directions. HEAD metamodel characteristics can be summarized as follows [3]:  
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* Unify the heterogeneous concepts of policy models. * A new generic metamodel that is able to include the heterogeneity of the existing models and the proposed metamodels. * Dynamic with the ability to create any needed component/attribute and the relationships between them. * Extensible metamodel where any derived AC model can be extended and upgraded. * Unlimited levels of components hierarchy. * Allow instantiating non-existing AC models. However, the contribution of this paper can be summarized as follows:  
* Provides a complete plan for a distinct AC framework starting from the metamodel development phase and reaching to the policy enforcement phase. * Opens new opportunities to develop and enhance the necessary services to answer the challenging AC requirements of today's computing environments based on distinct design and advanced AC metamodel. * Assists developers and security experts to include unified and generic components in designing secure ISs that conform to the organizational AC security policies. The remainder of this paper is organized as follows. In Section 2, we present the AC challenges of today's computing environments. The development stages of AC methods starting from common models reaching to AC metamodels, which is a recent research topic in the domain, are summarized in Section 3. In Section 4, we illustrate and explain the issues and limitations of the existing AC metamodels. In Section 5, we describe our development approach, the achieved steps, and the remaining ones, starting from the HEAD metamodel development phase and reaching to the policy enforcement phase. In Section 6, we explain the new opportunities this approach opens and what essential services can be developed based on the HEAD metamodel. Section 7 concludes this paper.