Designprinciples
Eleven principles for any design, from the first sketch to the finished build. The first ten are qualities to hold every design decision to. The eleventh, is what you get when you do.
Simplicity
Simplicity means fewer moving parts, fewer processes and fewer inputs. As the number of parts and processes increases, so does the probability of a mistake. Most mistakes are made when an overly complex system is forced to fit into a small space.
Ask What can we take out and still have it work?
Tension Flexibility — Each option added for a case that might come later is another moving part now.
Back to contentsStrength
Strength of design relates to the forces that it is capable of withstanding. Without sufficient strength, a design lacks durability and resilience. The stronger the design, the more stresses it will tolerate.
Ask What is the heaviest load this will carry, and what happens just past it?
Tension Economy — Strength costs material, and every saving on material comes out of the margin.
Back to contentsFlexibility
Flexibility is the ability to respond to change. If a design is not flexible, it will be brittle. A flexible design is one that can adapt to new circumstances and permits modifications.
Ask Which part will change first, and how much else moves when it does?
Tension Simplicity — A design that can adapt to anything carries parts for things it may never do.
Back to contentsReliability
Reliability is the ability to continue working under varying conditions. Reliability is related to strength and flexibility. A design without strength is not long-lasting and a design without flexibility has less ability to adapt; therefore, it will be unreliable when conditions change.
Ask Where will this be used that we haven’t tested?
Tension Performance — Tuning for speed in ideal conditions narrows the range of conditions it survives.
Back to contentsEconomy
Economy refers to a design that requires less resources and is scalable. With fewer necessary resources, the overall cost is lower, reducing waste and assuring affordability. Economy of scale means that as the system grows, and increases units in production, the lower the cost per unit of output.
Ask What does this cost at ten times the size?
Tension Strength — Taking out material takes out the reserve that absorbs the unexpected load.
Back to contentsPredictability
Predictability is the capability of the design to perform consistently over time. Predictability is also related to intuitiveness. The more predictable the design, the more likely it is that the design will perform as people expect.
Ask Would someone using this for the first time guess what it does next?
Tension Flexibility — Every behaviour that changes with context is one more thing a person has to learn.
Back to contentsPerformance
Performance is the capability of the design to run smoothly under demand. If a design cannot perform at the extremes of its capabilities, it is likely that the system is flawed. The more performant the design, the more likely the design will run without lag or latency.
Ask What happens on the slowest connection, at the busiest hour?
Tension Maintainability — Code tuned for speed is often harder to read, and harder to change.
Back to contentsSecurity
Security is the capability of the design to resist attack. If a design is not secure, some people will take advantage of it and others will be negatively affected. The more secure the design, the more likely it is that the design will keep people safe and protect what they hold dear – whether it’s their data, money, belongings, family, or their own personal safety.
Ask Who would want to break this, and what would they get?
Tension Accessibility — Each lock is a step someone has to get through, including the people it is meant to serve.
Back to contentsMaintainability
Maintainability is the ease with which a design can be changed, repaired, or upgraded. If a design is not maintainable, it may need to be replaced.
Ask Could someone new fix this without the person who built it?
Tension Economy — Building for repair costs more up front, and the savings come years later.
Back to contentsAccessibility
Accessibility is the capability of the design to be used by those who need it. The more accessible the design is, the more likely it will be used widely.
Ask Who can’t use this yet?
Tension Security — Every check that keeps the wrong people out can keep the right people out too.
Back to contentsOverall Quality
When these design principles have been thoughtfully applied, before and during implementation, the resulting design is more likely to possess overall integrity. The capability of the design to perform its purpose is assured because each part is held to a high standard, reflecting its level of quality.
Ask Which of the ten did we trade away, and did we mean to?
Tension All ten — The principles trade against one another, and quality depends on making those trades on purpose.
Back to contentsIn short
Start with simplicity, since a part that isn’t there can’t break, needs no upkeep and can’t be attacked. Then add strength where the loads are known and flexibility where change is likely. Together they give you reliability, a design that holds under load and adapts to change. Economy is the budget all the others draw on. Predictability can make up for some performance, because a wait people can see the end of feels shorter than one they can’t. Security and accessibility pull hardest against each other, so check every lock against the people it might keep out. Maintainability costs the people building it now and pays the people who inherit it later. Overall quality comes from making each of these trades on purpose, and writing down why.
Put them to work
Bring us a product, a site or an idea, and we’ll design it to these eleven principles.