Friday, January 17, 2014

What is quality?

Let us understand the concept of Quality. View the video that explains What is Quality or read on. Simply put, "quality" is a property or a characteristic of an item, a product, a service or a system. A physical product has properties like dimensions, weight, price or life span. Notice that each of these properties is one of two types, tangible or intangible. Properties like dimensions and weight are tangible. Meaning that they are physical properties that we can measure easily. Properties like price and life span are intangible. Meaning that they are not obvious to our senses or measuring devices. Quality is an intangible property of a product or a system. That is why it is not trivial to estimate it. It is probably impossible to measure it accurately.

What is quality?

Quality is relevant when considering any kind of a thing like a pen, a smart-phone, a vehicle or a software application. The perception of quality depends on the individual's preferences. For some, it can be meeting the specifications. For some, it is a large number of features. For others, it is the combination of other properties like performance, reliability, maintainability, security, portability, usability or aesthetics. High quality is naturally desirable to people. High quality means that the thing is better than its substitutes. Therefore, people tend to prefer items, products, services or systems with high quality. Manufacturers and service providers understand the users' preference for things of high quality.

A system can be specified by laying out its external features, inputs, internal processes, workflows, usage and outputs. For example, if you want to purchase a new car, you could look at the specifications of the model that interests you. You may want to see the dimensions, power, torque, seating capacity, fuel, engine type, driving features and so on. Then, figure if these specifications meet your requirements or not. As another example, consider an email application. Here, the specifications could be the type of email address, read email, write email, send email to one or more email addresses, include attachments and so on. Based on these specifications, you could estimate if this email application is suitable for you or not.

Another way of estimating the system quality is to look at the features. You could determine if there are many useful features in the system or not. For example, consider a calculator application. You could find if it has the basic features like addition, subtraction, multiplication and division. Then find if it has other useful features like sine, cosine, log, square root and so on. Then, figure if these features meet your requirements or not.

Yet another way of finding the quality is to examine other properties of the system. You could determine if it is fast (performance), able to work for long time (reliable), easy to repair (maintainable), safe (secure) and easily shifted from one environment to another (portable).

It is common to use any or all ways of estimating the quality. If the system meets the specifications, has a large number of useful features and has good performance, reliability, maintainability, security, portability, usability and aesthetics, it is perceived to be of a high quality.

Testing a system gives us data to estimate the quality of that system. Testing a system lets us know if the system meets each of its requirement specifications or not. It gives us data about working features of the system. It also provides data about other relevant system properties like performance, security and usability. Testing provides this data when the system is actually used. This why testing is so important. Especially software testing to estimate software quality.

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