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I have seen the proxy pattern being used before. It's quite nice as it create a foundation that you can build on. Requests can either be sent to the legacy syst

I have seen the proxy pattern being used before. It's quite nice as it create a foundation that you can build on. Requests can either be sent to the legacy system(s) or redirected to the new system (for new functionality/ fixes). Working with incremental changes, rather than trying to replace the whole system thing at once. The tricky part is dealing with more data silos. No one sets out to create a legacy system (maybe some consulting companies do), they just get more complex/ scary overtime. As the codebase and layers of technical debt are added, while documentation and the original creators disappear. I'd love to know the economic cost of businesses held back by legacy systems each year.

brudgers 12y ago
Just to clarify, one of the points that Eric Evans makes in the article is that programmers should set out to create legacy systems, because that means that they are really good at solving the business problems they are supposed to solve for a really long time. I used to think that an open source project that hadn't been updated since 2002 was inherently bad. Now I've realized that sometimes this means that it is just done and it's so simple that everything that has changed over the past decade is addressed by ./configure and make.