Skip to main content

The big three: Flexibility Extensibility Maintainability












[Time: 1 min 45 secs]


As we have said earlier, software is rarely ever made and forgotten. After the release, there will be change requests, there will be requests for new features, and bugs to be fixed. And why after the release, even when we are in the process of making software we have to interact with code that has already been written. It is with the goal of easing all of these, that we design software.

The design should enable flexibility, extensibility, and maintainability.













[Time: 9 mins]



FLEXIBILITY

  • What is flexibility?
  • Actions for change
    • Identify, Change, Test
  • Detractors of flexibility
    • Complex code
    • Lack of clear responsibilities for classes and methods
    • Unreadable code
    • Repetitions in code
    • Uncontained functionality
  • Design decisions that promote flexibility
    • DRY (Don't repeat yourself)
    • KISS (Keep it simple)
    • No tricks
    • Loose coupling
    • Encapsulation
    • Note: Minimize testing












[Time: 6 mins 25 secs]


EXTENSIBILITY

  • What is extensibility
  • Actions for extensions
    • Actions for change, adding classes
  • Detractors of extensibility
    • Same as detractors for flexibility (ideally we want to extend the software by adding new classes and not modifying existing classes)
  • Design decisions that promote extensibility
    • Loose coupling
    • Assigning proper responsibilities
    • Proper use of inheritance and polymorphism
    • Design patterns

MAINTAINABILITY:


  • Maintainability is flexibility + extensibility + bug fixes + refactorings

  • All design idioms for flexibility & extensibility apply to maintaibility also. Besides these design factors, some process factors like having proper test cases, and good documentation also apply. But since we are focussing on design in this section, we will not take any process related issues.
  • Remember "maintainability" is the ultimate goal of software design



Note: This post was originally posted on my blog at http://www.adaptivelearningonline.net

Comments

Popular posts from this blog

Running your own one person company

Recently there was a post on PuneTech on mom's re-entering the IT work force after a break. Two of the biggest concerns mentioned were : Coping with vast advances (changes) in the IT landscape Balancing work and family responsibilities Since I have been running a one person company for a good amount of time, I suggested that as an option. In this post I will discuss various aspects of running a one person company. Advantages: You have full control of your time. You can choose to spend as much or as little time as you would like. There is also a good chance that you will be able to decide when you want to spend that time. You get to work on something that you enjoy doing. Tremendous work satisfaction. You have the option of working from home. Disadvantages: It can take a little while for the work to get set, so you may not be able to see revenues for some time. It takes a huge amount of discipline to work without a boss, and without deadlines. You will not get the benefits (insuran

Testing Groovy domain classes

If you are trying to test Grails domain class constraints by putting your unit test cases in the 'test/unit' directory, then your tests will fail because the domain objects will not have the 'valdate' method. This can be resolved in two ways: Place the test cases inside test/integration (which will slow things down) Use the method 'mockForConstraintsTests(Trail)' to create mock method in your domain class and continue writing your test cases in 'test/unit' What follows is some example code around this finding. I am working on a Groovy on Grails project for a website to help programmers keep up and refresh their skills. I started with some domain classes and then moved on to write some unit tests. When we create a Grails project using grails create-app , it creates several directories, one of which is a directory called 'test' for holding unit tests. This directory contains two directories, 'unit', and 'integration' for uni

Some thoughts on redesigning education

Some time back I read a blog post on redesigning education. It asked some very good questions. Stuff which I had been thinking of myself. I left my thoughts on the blog, but I would also like to start a conversation around these ideas with those who read this blog as well. I would like to know what other people think of the issue of redesigning (college) education. I have often thought about how college education can be improved. To answer this question, we first have to ask a very basic question. What is the purpose of education? To me, we need education for 3 things: To learn more about the world around us To lead positive constructive lives To earn a good living / fulfill our ambitions I think education has to a large extent evolved to fulfill #3 (with a bias towards earning a comfortable living). The semester system, along with multiple choice tests, and grading, has made our education system into an assembly line. Students are pushed into the assembly line, given classes, admini