Ian Davis 2017 Spring c Ian Davis 1

© Ian Davis 2017 Spring (c) Ian Davis 1

The Mythical Man Month Design Essays on Software Engineering By Frederick P. Brooks, Jr 2017 Spring (c) Ian Davis 2

The mythical man month • The man-month as a unit for measuring the size of job is a dangerous deceptive myth. It implies that people and months are interchangable. • It takes 9 months to have a child, no matter how many women are assigned. • Brooks law: Adding manpower to a late project makes it later 2017 Spring (c) Ian Davis 3

A ship on the beach is a lighthouse to the sea • Moral: Learn from your own mistakes and from the mistakes of others Dutch Proverb 2017 Spring (c) Ian Davis 4

Good cooking takes time if you are made to wait it is to serve you better • Moral: Rushing things may be counter productive • Moral: Give people some time to excel Menu in New Orleans 2017 Spring (c) Ian Davis 5

Studies reveal large individual differences between high and low performers, often by an order of magnitude • Moral: Don’t assume everyone can do the same task in the same time • Moral: Always be asking how you can get 10 times more out of people by giving them tasks they are good at Sackman, Erikson and Grant 2017 Spring (c) Ian Davis 6

Reims Cathedral Guidebook This great church is an incomparable work of art. It was Jean d’Orbais who undoubtedly conceived the general plan of the building, a plan which was respected, at least in its essential elements, by his successors. This is one of the reasons for the extreme coherence and unity of the edifice. Moral: Respect the architectural rules in place Moral: Too many cooks making different soups spoil the broth 2017 Spring (c) Ian Davis 7

Add a little to a little and there will be a big pile • Moral: You can go a long way with small steps • Moral: Small mistakes here, and small mistakes there, quickly add up to a big mess Ovid 2017 Spring (c) Ian Davis 8

The Second Systems Effect • An architects first work is spare and clean. – He works carefully and fearfully with great restraint. • As he designs he notes frills and embellishments – These ideas get stored away for next time. • When completed the architect has become confident in their demonstrated mastery. – The second system is the most dangerous ever designed Fred Brooks 2017 Spring (c) Ian Davis 9

He’ll sit here and say “Do this! Do that!” And nothing will happen • • Moral: Talk is cheap Moral: Have to be able to monitor progress Moral: Not all who make promises keep them. Moral: There are limits to power Harry S Truman on Presidential Power 2017 Spring (c) Ian Davis 10

Why did the Tower of Babel Fail? They are just one people, and they all have the same language. If this is what they can do at the beginning, then nothing that they resolve to do will be impossible to them. Moral: Teams that communicate succeed. Moral: Teams that fail to communicate fail Genesis 11 2017 Spring (c) Ian Davis 11

Practice is the best of all instructors Experience is a dear teacher, but fools will learn from no other Moral: You can learn more by doing than reading Moral: What you don’t learn might cost you Publilus / Poor Richard’s Almanac 2017 Spring (c) Ian Davis 12

The Documentary Hypothesis Amid a wash of paper, a small number of documents become the critical pivots around which every project’s management resolves. This are a managers chief personal tools Moral: Know what is important and what is not. Moral: It is not the volume of paper that is important, but what is written on it. 2017 Spring (c) Ian Davis 13

Plan to throw one away It is common sense to take a method and try it. If it fails, admit it frankly and try another. But above all try something. Moral: An early start might not be helpful but not starting never is. Moral: Recognise your mistakes before they become costly ones. Franklin D Roosevelt 2017 Spring (c) Ian Davis 14

Sharp Tools A good workman is known by his tools Moral: Don’t reinvent wheels Moral: Knowing the tools can be as important as knowing the job Proverb 2017 Spring (c) Ian Davis 15

The Whole and the Parts I can call spirits from the deep. Why so can I and so can any man, but do they come when you call Moral: Saying you’ll do something, and doing it are two very different things Shakespeare 2017 Spring (c) Ian Davis 16

Hatching a Catastrophe How does a project get to be a year late? - One day at a time. Moral: Time management skills are central to successful software development Moral: Small slippages tend to become bigger ones Moral: Success has many friends, but failure is an orphan 2017 Spring (c) Ian Davis 17

What we do not understand, we do not possess Moral: Knowing must come before doing Moral: You can’t claim ownership of code you don’t understand Moral: Much of the challenge in design, is not the design but understanding how to design Goethe 2017 Spring (c) Ian Davis 18