Configuration management allows us to repeatably build product that can be delivered to the customer. In the hardware world, the "build" process is called "manufacturing" and the deployment is known as "shipping and installation." In the software world, our manufacturing is done through a build process, and our deployment is often automated, perhaps over the internet. However, unlike for hardware development, software teams continually build and rebuild the entire software product during development and can deploy these builds locally for verification. So the build process is not just a manufacturing process, but a development process as well. Deployment, during development, may involve deployment to the workspace area for developer testing, to a central test area, or to lab equipment. After that, there are still deployment considerations for verification, production certification, and finally to customers.

Build is central to CM. It's critical to do it right.

A basic build capability is founded on two key fundamentals: the ability to reproduce the build and the ability to automate the build process. Without these two fundamentals, you're fighting an uphill battle. Reproduction of the build implies that you have a CM system able to capture the build definition. Automation helps to ensure that no manual errors can play into the production. But this is just a basic build capability.

To move up the ladder, there's plenty more to be done. First of all, automation must be made available to all levels of the team, from production down to developer. Each member of the team needs the same assurance that the right stuff is being built: developer, integration, verification, production.

It's one thing to automate the build, but in a continuous or regular integration cycle, there could be a lot of work in deciding what's going into the build, especially in larger projects. So what's the secret to successful regular builds? Make sure you have quality going into the builds. To get a series of quality builds, it's important to make sure of two things: Start with a stable build and ensure the changes going into the build are of high quality.

If you've got a half-baked build to start with, don't open the floodgates for other changes. First, stablize the build through intensive debugging and changes that move the quality forward only. Once you have a stable build, you're in a good position for the second requirement—high-quality changes.

High-Quality Changes
High-quality software changes are a product of many factors: 

• Good people
• Good product architecture
• Effective peer reviews
• Feature and integration testing prior to check-in
• Ensuring the changes that go in are approved

Good people are hard to come by, but good processes, with a good mentor, can make average developers very effective. A mix of software experience, application experience, objectivity, and strong design and software engineering skills are desireable.

Good product architecture is key. I remember in my very first job, I had one week to get a code generator debugged and working. I looked at the architecture and it just wasn't there. The only way I could make the deadline was to throw out the existing work and rebuild from scratch; although, with a good bit of help from the existing work that had been done. The tactic was successful. Now, you might not want to throw out your entire flight software or telecom system, but if there are components that are overly complex and lack good architecture, your changes are going to cause problems. Your builds will have bugs that need to be ironed out before restoring a stable build, the first premise for the next build.

Effective peer reviews will eliminate a significant percentage of potential build problems, while at the same time helping to ensure that the architecture remains solid. It's important to have a good peer reivew process, but also a key developer involved, one who understands the architecture and and the wider issues involved. Peer reviews are most effective when they become a teaching tool—it's critical that new developers are aware of this going in.

Your process should not allow code to be checked in unless it has been tested. One of the most effective ways to ensure this is to track the test scripts, whether automated or manual, against the change, along with the test results. These should be reviewed as part of the peer review process. Another key practice is to include a demo as part of the peer review

Finally, it's important that there is control over what is going to go into a build. High-impact and high-risk changes should be accepted early in the process, before the full team begins working on the release cycle. Tight control must be exercised as release dates approach. It's fine to have a developer who can fix thirty problems a week, but if those are all low-priority problems and we're nearing in on the release date, the result may not be desireable. Typically, somewhere between 10 percent and 30 percent of problem fixes will introduce undesireable side effects. If only five of the problems really needed to be fixed for the release, there's a much better chance of not having a severe problem resulting. Still, if it's earlier in the release cycle, there's time to absorb such side effects and fix the problems before they go out the door.

When you're controlling what goes into a build, it is really ineffective to do so at build time. This will likely create a minor revolt among the developers, who have worked hard to complete their work. Instead, you want to ensure that change control is starting prior to assignment of changes to the design team members. Ideally, developers begin work by selecting tasks, problems, or features that have been approved and assigned to them. Then, there's no rejection of unwanted functionality or problem fixes.

Perhaps an even more critical side effect of having a change control process up front is that work flows from the developer through the process and into integration in pretty much the same order. This reduces the need for rollbacks, branches, and merges, and allows you to adopt a more optimized promotion scheme, ideally one where you don't even need to create separate promotion branches. This in turn makes it easier to automate selection of changes, as pre-approved changes can flow through the system as soon as they are successfully peer reviewed.

Manage the Superset Baseline, Build Subsets
Many organizations create and manage a baseline for every build. While this provides for full reproducibility, managing a large number of baselines can be complex. Typically a product has a number of variants. While it is important to try to move variant configuration into run-time or at least deployment, there are a number of cases where this is not or can not be done. In this case, the best strategy is to manage a superset from a baseline perspective, while building subsets. It's natural to configure a product from a subset of the baseline. Instead of dozens of baselines, a single baseline is used for management and reference purposes. Each build can be customized, as long as the CM tool tracks the build definition in terms of the baseline.

For example, build of the baseline with the English option; build of the baseline with European standards; build the baseline with a specific customization for NASA. Tracking of builds involves identifying the baseline, identifying the option tags, and identifying any additional change packages that need to be added to it. As emergency fixes are added, new builds can be easily readied just by adding in the change packages for those fixes. No need to specifically commission a new baseline.

At Neuma, we create baselines occasionally, and then create a series of regular builds off of each baseline, not just for customer delivery, but for "nightly builds." It's easy to look at the difference between builds just by looking at the changes that have been added to each. It's like building a new house by saying: "I want it just like that one but with these changes" instead of "Here are the complete plans for my house." Both will work, but in the former case we might say: "Let's bring the team in that built 'that' house."

What's in a Build
This leads us to a fundamental requirement. Although it matters less how you track a build (i.e., baseline + changes + options vs. new baseline), it is crucial that you can look at two builds and ask: What new features are there? What problems were fixed? How does it differ from what the customer currently has? What level of retesting is necessary? The Sikorsky S-92 helicopter was grounded with a requirement to replace the titanium studs in the gear box mounting with steel studs. No new baseline has to be established to correct the hardware. But a new build definition is needed for new craft. It may be due to a new baseline definition, or to an revised build process that says apply the following changes to the existing baseline.

The important thing in any case is that we can ask: what's in this build that's not in that build. I like a CM tool where I can take the customer's current build and then compare it interactively to various candidate delivery builds, just by scrolling through the candidate build list and then zooming in on the differences list for details. If, instead, I have to commission a team to describe the differences between every two builds, I've got a working, but painfully slow process.

Comparing builds is not just necessary for releases. If a key feature is noticed to have stopped working and I know it was working a month ago, I want to trace the changes build by build to see what functionality potentially impacted the feature. The more easily I can do this, the better. Traceability and zoom-in are critical. Similarly, these features will come in handy if a customer notices that something has stopped working. The ability for an orgainization to respond the same day, as opposed to days or weeks down the road, will make the difference between a happy customer and one that might be ready to take you to court. 

Getting There
Your current build process may be far from ideal. But if you can describe where you'd ideally like it to be, you can get there. There are numerous tools to help. There's plenty of expertise available. The demand for quicker turn around continues to grow, especially as competitive pressures continue to squeeze profits. Make sure your processes are moving to the next generation, and if they're already there, keep on moving.