This is Normalization rearing its head. A properly normalized database can be extended without needing refactoring and does not have modification anomalies. The

This is Normalization rearing its head. A properly normalized database can be extended without needing refactoring and does not have modification anomalies. There is a formal process to normalization. There is no such equivalent in code, but a poorly normalized data model virtually guarantees that any code wrapped around it will be messy. Conversely, mediocre code wrapped around a clean data model (less common in the wild) is much more amenable to incremental improvement.