| DisplayName | Description | ID | Base Class | Abstract | Hosted | Singleton | Group | Extension | Accessibility | ElementId |
![System.Reviewer](/images/ClassType.png) | Reviewer | Defines the basic properties of activity reviewers | System.Reviewer | System.SupportingItem | False | False | False | False | False | Public | 2f28a9ae-0e94-c895-c087-b222b231dd46 |
![System.WorkItem.Activity](/images/ClassType.png) | Activity | Defines the basic properties of activities that the system or user must complete for a change request | System.WorkItem.Activity | System.WorkItem | True | False | False | False | False | Public | 42642d4f-d342-3f1b-965c-628a0f4119e2 |
![System.WorkItem.Activity.AutomatedActivity](/images/ClassType.png) | Automated Activity | Defines the basic properties of automated activities | System.WorkItem.Activity.AutomatedActivity | System.WorkItem.Activity | True | False | False | False | False | Public | 25293e25-792e-1392-8ddc-3ae7f764fc8f |
![System.WorkItem.Activity.ContainerActivity](/images/ClassType.png) | Container Activity | Container Activity | System.WorkItem.Activity.ContainerActivity | System.WorkItem.Activity | True | False | False | False | False | Public | 65b9f85c-c8a5-858e-043c-460bbe3708f4 |
![System.WorkItem.Activity.DependentActivity](/images/ClassType.png) | Dependent Activity | Defines the basic properties of dependent activities | System.WorkItem.Activity.DependentActivity | System.WorkItem.Activity | False | False | False | False | False | Public | e786e1c7-b1fe-5b8b-ef8f-9e2dc346c44f |
![System.WorkItem.Activity.ManualActivity](/images/ClassType.png) | Manual Activity | Defines the basic properties of manual activities that a user must complete for a change request | System.WorkItem.Activity.ManualActivity | System.WorkItem.Activity | False | False | False | False | False | Public | 7ac62bd4-8fce-a150-3b40-16a39a61383d |
![System.WorkItem.Activity.ParallelActivity](/images/ClassType.png) | Parallel Activity | Defines the basic properties of parallel activities | System.WorkItem.Activity.ParallelActivity | System.WorkItem.Activity.ContainerActivity | False | False | False | False | False | Public | 568c49f2-d7d6-d7d7-89dc-dfb5b39fded7 |
![System.WorkItem.Activity.ReviewActivity](/images/ClassType.png) | Review Activity | Defines the basic properties of review activities that a user must complete for a change request | System.WorkItem.Activity.ReviewActivity | System.WorkItem.Activity | False | False | False | False | False | Public | bfd90aaa-80dd-0fbb-6eaf-65d92c1d8e36 |
![System.WorkItem.Activity.SequentialActivity](/images/ClassType.png) | Sequential Activity | Defines the basic properties of sequential activities | System.WorkItem.Activity.SequentialActivity | System.WorkItem.Activity.ContainerActivity | False | False | False | False | False | Public | 0ad0812b-f267-52bf-9f11-c56587786791 |