On Architecting: The Qualities

The first and most important step of software construction is the identification of the qualities that the software must possess. It is a step that can sometimes be overlooked or missed in the requirements process because we are often too eager to get into the details so that we can start building. We tell ourselves that "correctness," which is the quality that dictates software must correctly do what it is designed to do, is the end-all be-all upon which everything else hangs. And while this probably the most important quality to strive for in software construction, it is only one of many qualities that may be important to your client or customer.

As an architect, I have to understand the qualities that are most important to my client so that I know what my solution constraints are. There are a million ways to design a solution to any given software problem. It is my job as an architect to pick from that universe of solutions the one solution that most appropriately produces the qualities that matter the most. This task is a lot easier to accomplish when I know what those qualities are from the onset of a project.

Here are the top ten qualities that my clients generally desire when building solutions:

Adaptability	How easy should it be to change the software in the future? If you work in an environment where change is a normal part of the business process, then adaptability is probably important to you. Having worked on a software-as-a-service eCommerce platform before, I know a thing or two about how essential adaptable software can be for a clothing manufacturer trying to keep an edge on the competition. However, I've also worked in many enterprises where adaptability isn't very important at all because of time or budgetary constraints. Whether an application should be adaptable or not may drive whether you use the Adapter or Dependency Injection (DI) design patterns to build your system.
Availability	For how long does your application need to be available for your  users? Knowing the answer to this question will determine whether you will need to built in additional redundancy to ensure that the systems doesn't fail. You will also need to think about how to perform patching and feature upgrades without taking the system down for extended periods of time.
Correctness	Does the software do what it is designed to do? This is one of the more obvious qualities that most people would identify as being a very important. Hard to argue with the fact that, if software is being built for a specific set of jobs, it should do those jobs correctly.
Maintainability	Can other engineers easily support the system and perform debugging to resolve production issues? This quality makes it pretty high on the list for most engineers. With many shops being understaffed and strained for resources, it can be very important to customers to keep any learning curve associated with supporting the system at a very low level.
Robustness	How does the system respond to bad input or unexpected errors? An application designed to be used as a quick and dirty tool for an internal engineering team might not need to be very robust. However, an educational game designed to be used by hundreds of thousands of elementary school children might need to be very, very robust. Building robust software is not easy and will require very rigorous testing and software construction standards to ensure that a system can hold up when things take a turn for the worst.
Portability	Will the system need to execute across multiple platforms and devices? With the increase of phones, tablets, and other mobile devices, we live in a world where applications must often support multiple platforms simultaneously. Making a system portable requires a great deal of planning and consideration in order to determine what versions of each platform should be supported. There are a number of tools and frameworks that can assist with making applications more portable such as Java, Mono, and Silverlight.
Reusability	Will components implemented or used by the system need to be reused in other systems? When building a suite of applications that share the same features, reusability is an extremely valuable quality since it can save both time and money. Highly reusable components also ensure that your users will have a consistent experience from one application to another.
Scalability	Can the system perform well under increased load? Some systems do not experience the same load consistently from day to day or week to week. Systems and applications supported by a professional sports league will experience peak utilization while in season, demonstrating loads that are dramatically higher than they would be during the offseason.
Security	Is the system susceptible to attacks and intrusions? System security can be very challenging to design correctly. You have to think like a potential attacker, assess threats, and design the appropriate solution. There may be standards and regulations that must be adhered to in order to maintain certification. Whatever the case, security constraints should be examined up front since doing so too late will almost always be significantly more costly.
Usability	How well can users execute the various functions of the system? Users won't care what or how well your application works if they don't like using it. Applications that suffer from poorly designed user interfaces can double or triple the amount of work users have to do in order to use the system correctly, leading to big headaches for them and higher support costs for you.