# IT:AD:Functional Requirements #

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* See also:
    * [[IT/AD/Requirements/]]
    * [[IT/AD/Domain Functional Requirements/]]
    * [[IT/AD/System Functional Requirements/]]
    * [[IT/AD/Supplemental Specifications/]]
    * [[IT/AD/System Functional Requirements/]]
    * [[IT/AD/Non-Functional Requirements/]]



## Summary ##

{{page>IT:AD:Requirements:Diagrams#Requirements Diagram&noheader&nofooter}} 

Functional requirements are those that describe the Functions a System performs, as opposed to *Constraints* and *Qualities*, which are described in [[IT/AD/Supplemental Specifications/]].

It's important to understand that there are more than one kind of functional requirements.

Specifically, there are the following:

* Domain Functional Requirements:
    * This is what is most commonly understood as *Functional Requirement*, but there are also:
* System Functional Requirements.
    * Examples of System functionality that is in this set are:
        * DateTime Service
        * Caching Service
        * Host Settings Service
        * Settings Service
        * Data Persistence Service
        * Diagnostic Logging Service
        * Authentication Service
        * Authorisation Service
        * Auditing Service
        * Cryptographic Service
        * Help Service
        * Licensing Service
        * etc.