Tag Archives: LinkedIn

A Software Quality Model (Part I)

This is the first post, of more to come, about my thesis and the software quality model I have developed.

First I will explain in what context my thesis is placed. This post will focus on decisions made to actually form a ‘new’ model (actually, derived from…).

For my thesis I have investigated how to improve quality of a software product. The first step was to choose one of the five perspectives on quality, given by Garvin (see here for more information). The product based perspective is chosen for scoping reasons. With that perspective in mind, three software quality models where evaluated:

The first, and one of the most known models, is the model of Boehm (literally translated ‘the tree of Boehm’):

The second model was from Willmer and the third from Bemelmans. Basically Willmer takes Boehms model and took it a bit further in order to translate customer desires into metrics. Bemelmans takes a whole different approach: He takes three main characteristics: “requirements for usage”, “requirements for maintenance” and “requirements for product information”. Which each have their own sub-characteristcs. (though it does not look like a tree like Boehm, as it only has one dimension).

One model actually caught the attention because it tends to ‘translate’ customer language into a developer language. The basic idea is that a software quality characteristic is mapped with a metric. Unfortunately the book I had did not tell how to translate this. Also, there was a need to translate customer language into software quality characteristics. This was something that was not being explained either.

So how does the translation look like? Imagine a matrix, where at the left several software quality characteristics are given (for every row). And at the top, every column is a metric. With some means you could assign metrics to characteristics and get a basic idea what is important.

Taking the ‘translation matrix’ of Willmer as a starting point, I have developed a model that actually does three things:

1st. It translates customer language into software quality characteristics. Not only that, but it also gives a % of relevance. (more on that later).
2nd. The actual translation from characteristics to metrics. This looks a lot like how Willmer does this, but it also has a % per metric per characteristic.
3rd. The  interpretation of metrics. This is where things get really concrete. Here the actual scoring is defined. How will the metric LOC be interpreted?

With these three, it is possible to actually ‘calculate’ the total quality of a software product, with the ‘product based perspective’ of Garvin in mind! (So, it does not tell you how to improve your processes. Nor does it tell you how customers experience the website).

So how do you use this model? Using the “Plan/Do/Check/Act” (Circle of Deming) as basis, the suggested plan is:

– First ‘define’ quality.  (Plan)
– Meassure and analyse (Do)
– Evaluate (Check)
– Change definition / software (Act)

In my next posts I will explain briefly how the model looks like.

Choosing a Software Quality Model

For my thesis (Software Quality) I am currently figuring out how to choose a proper Software Quality Model in order to lay down the foundation of a Software Quality Definition for the project I am working on.

For now I have choosen this approach, and I’d like to hear from others how they (would) have tackled this problem.

It is good to know that I have narrowed down what “Software Quality” is. I’ll be focussing on the product (Garvin, Gosby) quality and the targetted audience are Software Engineers.

At first I will determine what kind of product I am working on. In this case it is a website, selling things. Some characteristics come to mind, like “24/7” or “should display always the correct (price) information”.

With these characteristics, I’ll look up Software Quality Attributes that would fit in.

This gives me a table, with in the first column all the characteristics, and next to them a few Software Quality Attributes that would fall into that specific characteristic description.

Now that I have a list of Software Quality Attributes, I can look up what Quality Model has the most matching Software Quality Attributes in them as well. Models that focus on different attributes would not interest me anymore, because it would not apply to the kind of product I focus on.

I found a nice model comparison, with Software Quality Attributes, from NASA. For your convenience I show it here:

With this, it would be possible to choose a Software Quality Model and work from there.

I am half-way with this method, and so far I think this is the way to go. If you think this is a bit too easy, or I should really take other considerations. Please let me know.

Note: thanks to Wouter for his suggestion who got me into this direction.

EasyMock Class Extension – IllegalStateException on expect method

When I write unit tests, I find using EasyMock extremely helpful. Especially using EasyMock Class Extensions give me the ability to mock objects which do not have an interface, or objects that are so legacy (and untested) that I don’t dare to touch them yet.

I say “yet” , because once I have reduced this ‘fear to break things’ factor by writing enough tests to ensure the legacy code works as it should, I *will* touch them.

One little piece of advice when writing your test, is that the ‘expect’ method will throw an exception when you tend to do that on methods that are final.

This might give you an IllegalStateException with the message : “no last call on a mock available”.

This basically means “Help I could not mock this call, and now you want me to mock it anyway!”.

Step back a bit and think how this EasyMock Class Extension would work in order to Mock existing classes? What would you do? Yes, you would extend this class, and override the methods!

That is what the EasyMock Class Extension does. So what happens when you make a method final? You cannot override it!

If you have any IllegalStateException from the EasyMock Class Extension, check your methods you tend to ‘expect’ (override) if they are marked “final”.

Remove the “final” keyword and you will be able to continue your work.

I’ll leave the question : “Should i just remove this ‘final’ keyword?” to your own wisdom…

Overriding and methods

Today I had a little challenge. I had a Class, I call it Class A. It has a method, i call it “doSomething”. Class B extends Class A, and overrides this method with a totally new behavior. Class C who extends from Class B wants to have the original behavior from Class A.

Here is a picture:

The Problem

Now, the simplest but most stupid way to solve this is using copy / paste. Yes, you simply copy the contents of the method of Class A and paste it into the method of Class C and you’re all set right?

Wrong!

It might work for a while, but one of the first things you *should* be feel itchy about, is code duplication! (along with its problems you get when you want to maintain your code).

So what now?

Solution : Use method for shared behavior

Solution : Use method for shared behavior

Well, when you took the easy road and duplicated your code, you probably wanted to get rid of that duplicate code immidiatly… And how do you do that? .. Yes,  you create a new method which is put in Class A , and accessible from Class C and Bam! Code Duplication gone, and you got what you want…

Another way is to re-think your class hierarchy. You might want to consider to do this:

 

Solution : Change in hierarchy, extend C from A, B from C

Solution : Change in hierarchy, extend C from A, B from C

 

 

Yes, you’ve seen it right. Perhaps you can swap Class B and C.  So C extends now from A, and B from C.

But, if you do that, be careful. You need to know exactly what kind of behavior you wanted in Class B. Most likely you have changed that now by extending from C. Take a good look at what methods B was originally calling from Class A, and if it now calls an overridden method by Class C.

These 2 solutions came up today. For my particular problem I’ve used the first. (no, not copy paste smart ass)

I think the first solution is the easiest, I would not recommend anyone to do the second solution unless you really know what you are doing. If you encounter more of these problems like above, swapping might be better for you.  

Do you got another (better?) solution? Let me know!

Game Programming (Experience)

Recently I saw at Youtube someone telling about his view on game programming. His targetted audience was for those who want to create games, but have no clue how to start. He began with something along the line of “I’ve been programming games for 5 years, so I guess I could say I’m experienced“.

That got me thinking. How long have I been programming (for) games?

I’ve been working on Arrakis since I was around 14/15 years old. I’ve finished it when I was 18. Arrakis is written in Basic (using Quick Basic 4.5). I realized in order to get further I had to learn a new programming language. One that did not had the limitations as Basic. Thats when I had decided to learn C. My first attempt was writing a new Dune II clone, this time really using the Dune II graphics.

After a short period of learning C I began playing around with the Half-Life SDK; I’ve been toying around with a bot framework (Botman’s bot) and before I knew it, RealBot was born. RealBot has been developed for around 4 years.

And, to complete the circle; while RealBot was fading away I picked up again my Dune mania and recreated Dune II – The Maker from scratch. 

Today, I am 26 years old. I haven’t worked on Dune II – The Maker seriously since 2006. This would mean I would have rougly around 7 to 8 years “experience”.  So considering that, I might also say that I have experience in game programming.

When you look at my LinkedIn, you see none of those projects counted as experience. Sure, they are mentioned
under “websites”. But I would prefer to put them in a more suited spot. Perhaps somebody has a suggestion for that.

Although ~ 8 years might sound like a lot. I do think it has to taken with a grain of salt.

First, I did not work 8 hours a day, 5 days a week.
Secondly, I did not have any sparring partners,  so quality wise I did not write superb code.

However, there are concepts that I’ve learned; and you only learn those when you write games. Concepts like:

  • sprite/bitmap management
  • drawing maps / tile engine
  • A*
  • parsing files (from original game)
  • little AI, 
  • state machines, 
  • double buffering
  • blending techniques
  • team colouring (in RTS)
  • using colorkey’s
  • transparancy
  • palette manipulation

And probably a few other things I can’t recall at this moment.

So yeah, perhaps I could say I do have experience in Game programming…