Wednesday, October 11, 2006

And a few more (maybe)

While discussing goals of software design with other developers, a few more potentiall goals came up. They were, robustness, correctness, time to market, staying in tune with team capability, reusability, efficiency, and usability. After some analysis (in my opinion) only reusability passed the test of whether something is a goal of software design. I used a simple test - if we can use design principles like loose coupling, etc to enhance the candidate and if we (almost) always want it as an end result of software development, then the candidate passes the test for a software design goal.

So, as of now reusability defenitely is a design goal. We achieve it by following the DRY principle. Any code that needs to be called accross methods in a class should be factored into a seperate method in that class, and any code that needs to be called accross classes, should be factored into a seperate class. This is reusability from an object oriented design perspective, but it can be taken further by creating reusable components. For example if we are building a web application, in all likelihood the authentication code will be needed by other web applications as well. We make it reusable by creating an Authentication component, by packaging all authentication classes into the same package heirarchy and creating a facade class that can be used by client code. The facade class should ideally implement some standard authentication (or a well thought of API in case a stadard does not exist) API, to enable users to swap it with another authentication component.

Thats it about goals of software design. Do write back with your thoughts, perspectives, and queries. 

Note: This post was originally posted on my blog at

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