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  • Data duplication is A Bad Thing en.wikipedia.org/wiki/Third_normal_form Commented Feb 20, 2015 at 15:13
  • Most definitely, but I'd like to keep things separate from each other, such as user data and contact (CRM) data. Is data duplication allowed in these instances? Commented Feb 20, 2015 at 15:16
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    Data duplication is not always a bad thing, decoupling might be sometimes a serious reason to duplicate data when having careful designed synching mechanisms. But when designing a business model for an ERP system from the ground, as shown here, I would avoid any redundancy as hell. And do yourself a favor, read martinfowler.com/apsupp/accountability.pdf first before reinventing the wheel. Commented Feb 20, 2015 at 15:36
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    As someone who has actually worked as a DBA on RDBMs with billions of rows, denormalisation is sometimes a necessary evil for performance reasons. However, that is primarily an implementation concern (what we used to called physical design). You should aim to eliminate any data duplication in the initial (logical) design. Commented Feb 20, 2015 at 16:38
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    Could you substitute that mind map with a Crow's foot ER diagram? Example: upload.wikimedia.org/wikipedia/commons/9/91/… Commented Feb 21, 2015 at 0:26