Hi, I've just started a small web app, and I am using an ORM product for DB access, which is what I have been doing for the last 5 years. In the beginning I had my own solution, but after leaving the company I wrote it for, I did not take the code with me, and great products emerged for .NET like llblgen. The thing is, for a small project, it is almost inevitable for a developer to quickly create a db schema, generate sql statements from the db design tool, and create the db, which if followed by reverse engineering the db with orm tools, and bind it to UI. It is the kind of thing that I've done maybe a hundred times or more. The thing is, when I start with use cases, and a domain model that does not include any concerns for persistence, the results are different. The uml diagram I'm looking at uses inheritence, design patterns etc, and if you do not think about persistence, the look of the code that uses this model is quite clean. It is more maintainable too. Now this is a clash between two different approaches, where domain info is modelled first in db or in a domain model. The question is, what is the best way to merge these approaches? I am really happy about using benefits of OO in the domain model, but at the end I find myself writing a "manager" layer which connects domain classes to orm generated classes. I am not sure if ORM should be responsible for more than eliminating the gap between relational paradigm and OO paradigm, and you see all these resources referring to ORM classes as domain classes. Check out any OO design resource or course, and you'll see that the modelling of a domain is rarely performed in DB world, where schemas and allowed db types are your building tools. Eclipse Modelling Framework seems to have a binding to Hibernate for example, which is a clear indication of seperating domain model from ORM classes, and I think I am in favor of this approach, for it allows me to do the design based on OO approach, and it also gives the benefit of being able to isolate myself from sql. On the other hand, ORM based approach simply works! I think I'm more inclined to accept ORM (generated) classes as domain classes when I'm under time pressure and the app is small, and writing down the connecting layer between domain and orm layers when I have more time and the project is larger. I'd love to hear what you think about this. How do you draw the line? Which approach is common in your shop?
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