# FAQs

* [What are Concrete Domains?](https://docs.snomed.org/snomed-ct-user-guides/authoring-user-guide/faqs/concrete-domains)
* [What is Description Logic (DL)?](https://docs.snomed.org/snomed-ct-user-guides/authoring-user-guide/faqs/description-logic-dl)
* [What is the Machine Readable Concept Model (MRCM)?](https://docs.snomed.org/snomed-ct-user-guides/authoring-user-guide/faqs/machine-readable-concept-model-mrcm)
* [What are Project Branches, Task Branches and Rebasing?](https://docs.snomed.org/snomed-ct-user-guides/authoring-user-guide/faqs/project-branches-task-branches-and-rebasing)
* [What is the Reporting Platform (RP)?](https://docs.snomed.org/snomed-ct-user-guides/authoring-user-guide/faqs/reporting-platform-rp)
* [What is Role Based Access Control (RBAC)?](https://docs.snomed.org/snomed-ct-user-guides/authoring-user-guide/faqs/role-based-access-control-rbac)
* [What are Service Acceptance Criteria (SAC) and Authoring Acceptance Gateway (AAG) controls?](https://docs.snomed.org/snomed-ct-user-guides/authoring-user-guide/faqs/service-acceptance-criteria-sac-and-authoring-acceptance-gateway-aag-controls)

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