The need for quality of Web Applications

I’ve been working on my thesis (about meassuring Software Quality) and its reaching its final state. I will blog some posts about my thoughts and findings about Software Quality from here. This post was a bit old, I dusted it off and actualised it a bit. More to come!

Here it comes:

Today, it is unthinkable to not use an internet related service in your daily life. Think about staying in touch with family and friends using email (gmail, yahoo, hotmail, etc), social networking (twitter, facebook, hyves, etc) or more.

If you want to book a trip, you arrange this using the internet. When you want to buy a new laptop, you find the specs and reviews on the internet. You use a comparison site to find the cheapest (web)store. And if you want to buy it, you use the internet.

It is fair to say that the internet has become more and more important to our lives. Even more than we imagined 5 years ago. How would we deal when our mail provider is down? How would we react when facebook is down? What about twitter? How do we do our bank business when we cannot reach the online-banking site?

I think you got the point.

Companies developing and maintaining (ecommerce) websites or services are constantly pressured to deliver high quality software in the shortest possible amount of time. Having these factors, time and quality; one cannot exclude the other. They do influence each other though. When you want to deliver fast, you ought to make sacrifices in terms of designing and testing the product. This will eventually lead to a lower quality. The opposite is true as well, if you spend more time in the design and testing, you will likely deliver higher quality. Also, unlike with traditional software, it is not always the first to deliver that is the best.

In the land of the internet, it is not only the case to get users to your website, but also to keep them revisiting. If you deliver a fancy new feature, you might get the attention. But if you did not put enough effort to make it high quality, you might lose them to your competitor who delivers a similiar feature a few days later, but twice as good. Remember, your visitors can easily switch if you cannot deliver what they expect.

So what does a visitor expect from a website? Looking around on the net you can find some definitions of quality of good websites. That is the biggest question of all. How can you deliver fast, and yet have some sort of quality to rely on?

You could use a Software Quality Model for that, like the ISO-9126. I would say, you’d use a model like the ISO-9126 and create/use a Web Application Quality Standard.

So what is this standard? I haven’t found a definite model, although I have found a good resource here.
In my opinion, the following Software Quality Attributes would belong in such a model:
performance. Your visitors will leave if loading a page takes longer than 2 seconds. Directly influencing possible sales!
security. Atleast be aware of the top ten of OWASP. Better yet, make sure you are not vulnerable to these exploits.
maintainability. Developers should be able to easily extend code, or fix bugs without causing too much regression.
reliability. Should your website simply shut down once the load is too high? How much ‘page faults’ may appear? One of thousand requests? One of hundred?.

Each of these attributes can be split into several measurable units. For example, performance wise you could measure the amount of time it takes to get a page loaded in the browser. Maintainability has some known measures (like McCabe’s Cyclomatic Complexity).

Note: Recently I figured that the ISO-9126 is actually not a model, but a ‘standard’. It really does not tell you *how* to do things, but it does give guidelines. The Software Quality model I’ve made does tell  you how to do things.


  1. you mention the four software quality attributes applicable. Remember that 9126 was designed back in the late 80s (see SQE book for a good background and explanation).
    Every since, we’ve been using the model but interpreting the attributes for realtime systems and then for SOA/web based apps.
    Should probably extend this to iphone apps etc

  2. I bet more attributes could be applicable. In fact, I dare to say a lot of attributes are applicable in a sense.

    The model I’ve worked out is derived from Willmer (which is basically a version of McCall et al, but adding a ‘translation’ from user requirements to developer terms (quality attributes).

    Perhaps there needs to be an ISO standard for web based applications. As they are still being treated as ‘normal’ applications (system components, etc). In a way they are, but then again the environment they operate in is totally different.

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