Adaptive Software Solutions

A few days back, while reviewing some code I came across what I considered to an over abundance of assumptions in infrastructure code. Such assumptions in infrastructure code can make software buggy and difficult to change. Let me first explain what I mean by infrastructure code. Frameworks always have interactions that we use when we extend their classes. For example if you have used Struts, then the custom action classes we create, use Strut's infrastructure code from the ActionServlet and the Struts RequestDispatcher. These classes call methods which are overriden by our custom classes, thus allowing our code to get called. Even when we do not use such frameworks, there are lots of places where we have hand written infrastructure code in our projects. Typically these are methods in base classes that are invoked as part of a use case. These methods will do a bunch of things that are determined by reading configuration files, decoding the request that invoked them, and perhaps oth...

In this section we will take a requirements document for a software system and create a system design from it. The statement for the excercise has been inspired by Dave Thomas' coding kata #1 . Let's build a system for a supermarket. Here are the requirements. The supermarket has various items for selling. Each item has a price. Sometimes an item may have a discounted price, and sometimes it may be part of a scheme. Schemes could be similar to buy two get one free, or buy a certain quantity of an item and get another item free. Items may also be priced for a certain unit. For example Apples may be Rs 40/Kg, however they can be sold in a fractional unit also 500 gms. Some items may be simple, like a can of Pepsi or complex like a crate of 10 Pepsi cans. The sytem should also maintain an audit trail of all sold items for future evaluation. The store manager should be able to get a valuation of the current stock. When a shopper checks out items the system should calculate the most...