One of the valuable ideas from Frederick Brooks' classic The Mythical Man Month is the notion of the second system effect when designing software systems. The following is an excerpt from the book where the concept is introduced

An architect’s first work is apt to be spare and clean. He knows he doesn’t know what he’s doing, so he does it carefully and with great restraint.

As he designs the first work, frill after frill and embellishment after embellishment occur to him. These get stored away to be used “next time.” Sooner or later the first system is finished, and the architect, with firm confidence and a demonstrated mastery of that class of systems, is ready to build a second system.

This second is the most dangerous system a man ever designs. When he does his third and later ones, his prior experiences will confirm each other as to the general characteristics of such systems, and their differences will identify those parts of his experience that are particular and not generalizable.

The general tendency is to over-design the second system, using all the ideas and frills that were cautiously sidetracked on the first one.

In my experience, the second system effect doesn't just come into play when the creator(s) of the second system also worked on the first system. In many cases, a development team may be brought in to build a new version of a first system either because they are competitors trying to one up a successful product or they are building the next generation of the technology while the original team goes into "maintenance mode" (i.e. shades of The Soul of a New Machine). In such situations, the builders of the second system can fall into the trap that Frederick Brooks describes in chapter 5 of Mythical Man Month.

At almost any point in time over the past few years, I could easily count about three or four software projects I was personally familiar with that were making classic "second system" mistakes. However instead of vilifying these projects, I thought it would be useful to list the top three things I've seen that have separated second systems that have avoided falling into this trap and those that haven't.

Realize You Can't Do It All In One Release

A lot of projects lose their way because they try do a too much in a single release. As Raymond Chen wrote You don't know what you do until you know what you don't do. Until you start focusing on a key set of scenarios your product will nail and start cutting features that aren't necessary to hitting those scenarios, your project isn't ready for prime time. What developers often fail to remember is that there is always another version and you can fit those scenarios in at that point.

One company that gets this idea very well is Apple. I can still remember Cmdr Taco's infamous review of the original iPod when it ran in 2001; "No wireless. Less space than a nomad. Lame." However the iPod nailed its key scenarios and with that success kept expanding its set of key scenarios (more space, video, photos, etc) until it became the cultural juggernaut it is today. You can see the same qualities in the iPhone. Just a few months ago, you'd read articles like Final report: The iPhone is not open for business that argued against the iPhone because it didn't support 3G, lacked Exchange support and had a non-existent developer platform. However the original iPhone was still successful and they addressed these issues in the next version to even greater success.

You Can be Date Driven or Feature Driven but not Both

A date driven release is one where everyone on the team is working to hit a particular time cut off after which the product will ship with or without their feature. Software products that have to hit the back to school cycle, tax time or the holiday shopping cycle are often date driven. A feature driven software release takes the "we won't ship it until it is ready approach" which is popular among Open Source projects and at companies like Google (according to Steve Yegge).

The thing to note about both approaches is that they are built on compromise. In that, we will compromise on our ship date but not on our features or vice versa. Where software projects tend to go awry is when they decide to be both feature driven and date driven because it means they have left no room to compromise.  This is additionally problematic because we are so poor at project estimation in our industry. So at the start of a project you have features that should take a two years to ship only budgeted as needing a year of work. In a date driven release, once this discrepancy is realized it is at that point features start getting cut or "placed below the cut line". In a feature driven release, the ship date is adjusted and ship expectations adjusted.

Projects that are both feature driven and date driven (i.e. we have to ship features X, Y & Z on date A) end up delaying these decisions until the last minute since they aren't mentally setup to compromise on either the date or the features. So they end up doing neither until the very last minute. This leads to missed deadlines, hastily cut features and demoralization within the product team. This often continues for multiple deadlines until finally the project team gets to the point where they feel they must show something for all the missed deadlines and cut features by throwing together a mediocre release after the one too many missed deadlines. We've all seen software projects that have succumbed to this and it is a sad sight to behold.

Don't Lose Track of What Made the First System Successful

Developers tend to be a fairly critical lot so when they look at a successful "first system", they often only see the flaws. This is often what fuels the second system effect and leads to losing sight of why the first system became a hit in the first place. A recent example of this is the search engine Cuil which was started by some former employees of Google with the intent of building a search engine which fixes the issues with Google's search engine. Unfortunately, they had a disastrous product launch which has been documented in blog posts like How To Lose Your Cuil 20 Seconds After Launch and news articles such as Cuil shows us how not to launch a search engine.

When you look back at the PR buildup leading to Cuil's launch, it is interesting to note that even though the Cuil team dubbed themselves Google slayers they did not address the key things people like about Google's search. Google's search provides relevant search results as quickly as possible. Cuil bragged about providing more complete results because their search index was bigger, showing more results above the fold by going with three columns in their search engine results page and that it offered richer query refinement features than Google. Although all of these are weaknesses in Google's user experience they are trumped by the fact that Google provides extremely relevant search results.  The Cuil team lost sight of this, probably because working at Google they only ever talked about fixing the flaws in the search product instead of also internalizing what has made it so successful.

This is an extremely common mistake that cuts across all categories of software products.

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