Winning the stern chase

A "stern chase" is a race between two competitors, where one is following the other. The leader's goal is to stay ahead; the laggard must overtake the leader. Both positions have challenges: the leader is ahead but has less information (he can't see the follower), the laggard must work harder but has the advantage of seeing the leader. The lagard knows when he is gaining (or losing) the leader, and can see the actions taken by the leader.

In software, a stern chase occurs when replacing a system. Here's the typical pattern:

A company builds a system, or hires an outside form to build the system. The new system has a nice, shiny design and clean code (possibly). Over time, different people make changes to the system, and the design degrades. The nice, shiny system is no longer shiny, it's rusty. People dislike the system - users don't like it, nor do developers. Users find it hard to use, and developers find it hard to modify.

At some point, someone decides to Build A New System. The old system is buggy, hard to use, hard to maintain, but exists and gets the job done. It is the leader. The new system appears shiny but has no code (and possibly no requirements other than "do what the old system does"). It is the laggard.

The goal of the development team is to build a new system  that catches the old system. Thus the stern chase begins. The old system is out in front, running every day, and getting updates and new features. The news system is behind, getting features added but always lacking some feature of the old system.

Frequently, the outcome of the software stern chase is a second system that has a design that is (eventually if not initially) compromised, code that is (eventually if not initially) modified multiple times and hard to read, and a user base and development team which are (eventually if not initially) asking for a re-write of the system. (A re-write of the new system, not the old one!) The stern chase fails.

But more and more, stern chases are succeeding. Not only succeeding in the delivery of the new system, but the succeeding in that the replacement system is easier to use and easier to maintain.

A stern chase in software can succeed when the following conditions exist:

The chase team knows the old system the problem domain, and has input into the design of the new system. The team can contribute valuable insights into the design for the new system. The new system can take the working parts of the old system, yet avoid the problems of the old system. This lets the development team aim.

The chase team uses better technology that the old system. Newer technology (such as C# over C++) lets the chase team move faster.

The chase team uses a process that is disciplined. The biggest advantage comes from automated tests. Automated tests let the chase team re-design their application as they move forward and learn more about the problem. Without automated tests, the team is afraid to make changes and try new designs. It's also afraid to clean up the code that has gotten hard to maintain. (Even on a new project, code can be hard to maintain.)

With these conditions, the chase team moves faster than the team maintaining the old system. In doing so, they surpass the old system and win the race.