# HEAD Access Control Metamodel: Distinct Design, Advanced Features, and New Opportunities
## 6 Open Issues and New Opportunities  
The emergence of new technologies, especially IoT and industry 4.0 systems, needs the application of robust and advanced security mechanisms. However, security models and AC solutions were not developed to address the current challenges of highly dynamic environments. They are not able to meet the needs of transparency, scalability, shareability, interoperability, and end-to-end security. Accordingly, several studies confirm that a deep revision and adaptation of those mechanisms need to be considered [41, 42]. In this paper, we present a development approach in AC for complex, dynamic, and heterogeneous environments. The characteristics of the HEAD metamodel, and the development approach for its phases, explained in Section 5, allow developing essential issues in the domain and it opens new opportunities and various research directions which will be summarized in this section. Hence, having an advanced AC metamodel, that is generic, dynamic, extensible, and supports the hierarchy of components, allows for developing and integrating various other important issues such as:  
* HEAD metamodel could be enhanced to dynamically generate AC policies according to users' context, profile, device, etc., since is based on a multi-level rule engine.
* In collaborative computing environments, distributed multiple cyber-physical areas interoperate with each other to provide an intelligent environment for users to achieve their collaborative activities. Hence, the features of the HEAD metamodel would facilitate fulfilling the collaboration and interoperability between the derived and heterogeneous AC models and their components among distributed multiple cyber-physical areas.
* The continuous technology upgrades impose the need to migrate AC policies from one model to another. The HEAD metamodel supports all the necessary tools to enhance with this new feature, in addition to its features.
* HEAD metamodel could be enhanced to implement and include built in packages or set of tools with predefined AC models, for example, the most used models DAC, MAC, RBAC, and ABAC. This could minimize the technical implementation efforts and facilitate administrative efforts to define policies.
* Since the definition for hundreds of thousands of attributes, expressing rules and policies, and performing implementation require a lot of time and resources, artificial intelligence (AI) techniques could be used, for example, object recognition to identify objects and define their attributes. Hence, the administrator could modify, add, or remove some attributes instead of creating hundreds of objects and thousands of attributes, especially in very large and complex systems.
* It could be enhanced and implemented to extract the data flow of an organization to define the rules after extracting the entities and attributes, then the administrator could be notified if there are some missing rules that must be defined.
* The features of the HEAD metamodel allow integrating AC to other systems, for example, intrusion detection systems.
* The flexible, upgradable, and dynamic nature of the HEAD metamodel makes it adaptable and applicable to distributed systems; hence, it allows developing and implementing blockchain-based AC systems.  
Each of the above points is itself an opportunity (in addition to many other opportunities) for enhancing AC in today's computing environments using a unifying framework. In summary, the HEAD metamodel contributes to the development of knowledge in the field and can be considered as a paradigm shift toward reshaping the existing models and AC methods, especially in the field of industry.