Peter Gillard-Moss is a ThoughtWorker and general memeologist living in the U.K. He has worked in IT since 2000 on many projects, from public-facing websites in media and e-commerce to rich-client banking applications and corporate intranets.
IT WILL NEVER LOOK LIKE THAT. It is all too easy to fall into the trap of investing large amounts of time in a design and being confident that the implementation will come out the same. A detailed design can easily fool you into believing you have every angle covered. The greater the detail and the more in-depth the research, the greater your confidence in it. But it is an illusion: it will never look like that.
The truth is, no matter how in-depth, how well researched, and how well thought-out your design, it will never come out looking the same as in your head. Something will happen, an external factor may affect the design: incorrect information, a limitation, an odd behaviour in someone else's code. Or you may have got something wrong: an oversight, an incorrect presumption, a subtle concept missed. Or something will change: the requirements, the technology, or someone may just find a better way™.
Those minor alterations in the design soon stack up and lots of minor alterations soon require that one big one has to be made. Before long your original concept is on the floor in pieces, ...