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Are there really no instances of rewrites succeeding? Are we sure that projects that failed doing rewrites wouldn't have failed more painfully if they'd continu

by T-R 14y ago

Are there really no instances of rewrites succeeding? Are we sure that projects that failed doing rewrites wouldn't have failed more painfully if they'd continued dealing with the cruft of the old codebase? It's possible the problem is more in how these projects went about their rewrites, than just the fact that they did. What was the scope of the rewrite - did they simultaneously re-architect, redesign the UI, and try to implement all their hoped-for features (second-system effect)? Did they try to re-use old modules (temporarily or permanently - did they not reuse enough, or did they invest too much time making old code compatible)? Did the entire team immediately switch over to working on the rewrite, or did it get too few resources? It might be worth investigating how a rewrite could possibly be done successfully, instead of assuming that the only option is to slowly refactor.

dasil003 14y ago
It depends on the individual case. It's not always possible to isolate subsystems in order to refactor incrementally, but on the other hand it's also almost certainly a foregone conclusion that you will underestimate the complexity of a rewrite.
lobster_johnson 14y ago
> Are there really no instances of rewrites succeeding? The most famous instance of a successful rewrite was IBM's transition to OS/360 [1] in the 1960s, which was not just a complete rewrite but a completely new system to replace all the previous ones. (The "360" comes from the number of degrees in a full turn.) Who spearheaded this huge effort? A certain Frederick P. Brooks, who used his experience with the project to write _The Mythical Man Month_, which coined the term "second-system effect" [3]. Of course, while the 360 project was _ultimately_ successful, they made all the now-familiar mistakes that Brooks documented in his book -- it was an extremely expensive and time-consuming project that was only possible thanks to IBM's enormous resources and strong leadership. --- [1] http://www-01.ibm.com/software/os/systemz/pdf/360Revolution_0406.pdf http://www-01.ibm.com/software/os/systemz/pdf/360Revolution_... [2] http://en.wikipedia.org/wiki/The_Mythical_Man-Month http://en.wikipedia.org/wiki/The_Mythical_Man-Month [3] http://en.wikipedia.org/wiki/Second-system_effect http://en.wikipedia.org/wiki/Second-system_effect

by T-R 14y ago

dasil003 14y ago

It depends on the individual case. It's not always possible to isolate subsystems in order to refactor incrementally, but on the other hand it's also almost certainly a foregone conclusion that you will underestimate the complexity of a rewrite.

lobster_johnson 14y ago

> Are there really no instances of rewrites succeeding? The most famous instance of a successful rewrite was IBM's transition to OS/360 [1] in the 1960s, which was not just a complete rewrite but a completely new system to replace all the previous ones. (The "360" comes from the number of degrees in a full turn.) Who spearheaded this huge effort? A certain Frederick P. Brooks, who used his experience with the project to write _The Mythical Man Month_, which coined the term "second-system effect" [3]. Of course, while the 360 project was _ultimately_ successful, they made all the now-familiar mistakes that Brooks documented in his book -- it was an extremely expensive and time-consuming project that was only possible thanks to IBM's enormous resources and strong leadership. --- [1] http://www-01.ibm.com/software/os/systemz/pdf/360Revolution_0406.pdf http://www-01.ibm.com/software/os/systemz/pdf/360Revolution_... [2] http://en.wikipedia.org/wiki/The_Mythical_Man-Month http://en.wikipedia.org/wiki/The_Mythical_Man-Month [3] http://en.wikipedia.org/wiki/Second-system_effect http://en.wikipedia.org/wiki/Second-system_effect