> For the complete documentation index, see [llms.txt](https://appmaster.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://appmaster.gitbook.io/docs/data-design/data-models-designer/system-fields.md).

# System fields

Working with the data model designer.

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Within each new data model, **system fields** are created by default: 

* **ID** (unique identifier for the model); 
* **CreatedAt;** 
* **UpdatedAt;** 
* **DeletedAt.** 

These fields are for tracking the life cycle and changes of data model records. They cannot be renamed or deleted but can be used to build business logic and user interface.

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