Single responsibility principle - Tea

I’ve been a long-time in technology development, and there are few theories that I take more seriously than the single responsibility principle. To best understand the features and benefits of this principle, you can consider a simple product, my preferred example is a mug of English tea.  Typically, tea has five parts (objects), the mug, the tea, the water, the milk, and the sugar. Each part has its own independent function, and while their combination provides an added value product, all are essentially independent.  

  • The mug serves as a vehicle to store the drink.
  • The tea provides the flavour.
  • The water provides the liquid solution.
  • The milk has traditionally been a coolant.
  • The sugar functions as a sweetener.
The success of tea
With any product, change is inevitable as technology and humanity advances.  Because the cup of tea benefits from the single responsibility principle it has survived as a product for over 300 years. Over this period, pressure from consumers has meant that mugs have changed style, shape, and materials, artificial sweeteners have been introduced to replace sugars, and the variety of milk, from full fat dairy, to light soy, is enough to make your head spin.  The real point here is that none of these five parts changed at the same time, or for the same reason.  More importantly, when, for instance, Soy Milk was introduced, no-one had to run a risk assessment, or ultimate modify any of the other parts.  In tea, milk has an independent function, if the user only wants to change the method of cooling, then only the milk is required to change.

There is a cost to adhering to this principle, or, put another way, tea can be produced cheaper.  Value solutions like Ty-phoo QT are technically advance, and I’m positive the creators thought themselves innovative and rather smart.  However, by combining the parts, change is impossible and not only does this limit future innovation, but also limits today’s market share. Besides, ultimately, product quality suffers. Keeping the parts independent just makes sense.