What is “train” based development?

Question

I ran across yet another new term in development methodology, and I haven't been able to find a definition for it. Specifically, it's called "train based development."

Here are some examples of where I have seen this term.

Earlier this week, I asked our engineering leads and release managers to take the Windows Metro version of Firefox off the trains. (Johnathan Nightingale)

https://blog.mozilla.org/futurereleases/2014/03/14/metro/

From the Mozilla careers web-site:

Experience working with both agile development methodology, and train-based development/QA teams.

I have heard of "train" before and not just in the context of Mozilla. But I haven't managed to find any good information about it on the net.

When I googled "train based software development", I found very little information in the search results. The closest that I could dig out that separates the train from the wagons is that "train" is about making releases at regular intervals according to a schedule. But it also seems that "train" is a sort of concrete QA setup.

So, what is "train based development"?

Answer 1

Summing up information from this blog :

• The analogy is trains are releases, passengers are features
• Trains are planned at regular intervals, without knowing what they will contain
• If features aren't ready for departure train, they can go on the next one
• Once a version is shipped, the development splits between support/patching shipped code and developing the next train
• This development is mostly aimed at large client softwares, rich in features, and broadly distributed such as a web browser or an OS, where old versions may stay active for a long time.