> For the complete documentation index, see [llms.txt](https://coldbox.ortusbooks.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://coldbox.ortusbooks.com/v6.x/the-basics/models/domain-modeling/data-layers.md). # Data Layers ![](https://github.com/ortus-docs/coldbox-docs/tree/97b8636ca1e8f4651f1021343c097bb3a7c2e9b9/.gitbook/assets/MVC%2Bobjects.png) If I know that my database operations will get very complex or I want to further add separation of concerns, I could add a third class to the mix: `BookGateway.cfc` or `BookDAO.cfc` that could act as my data gateway object. Now, there are so many design considerations, architectural requirements and even types of service layer approaches that I cannot go over them and present them. My preference is to create service layers according to my application's functionality (Encompasses 1 or more persistence tables) and create gateways or data layers when needed, especially when not using an ORM. The important aspect here, is that I am thinking about my project's OO design and not how I will persist the data in a database. This, to me, is key! Understanding that I am more concerned with my object's behavior than how will I persist their data will make you concentrate your efforts on the business rules, model design and less about how the data will persist. Don't get me wrong, persistence takes part in the design, but it should not drive it. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://coldbox.ortusbooks.com/v6.x/the-basics/models/domain-modeling/data-layers.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.