Saturday, April 24, 2010

4 Things That are Almost like Programming, but not quite

Do you sometimes struggle in explaining your work to others? Especially at project planning time, I sometimes reach for metaphors to explain why estimating can be hard. Here are a few of the metaphors I've used in the past, and a few reasons they aren't adequate.

Building a house or bridge
This is a common analogy, and one often used by those that believe programming is 'engineering'. It's true that you can break the problem down into smaller pieces, then plan constructing the pieces. Repeat this cycle, going into ever greater detail, until you have your 'plan'. In this way, construction is similar to traditional 'waterfall' methodologies. There are similarities to 'agile' practices, too. A house is built iteratively-- you pour the foundation, then put up the framing, then the roof, etc. At any point along the way you can evaluate and make small changes as you go.

But.... a building is a lot more like other buildings than one computer program is like another computer program. We've been building houses and bridges for centuries, and there are only so many variations among them. Programs, on the other hand, have only been built for about 50 years and they have a lot more variables that can change. Programs also have temporal issues to deal with-- the order of things happening must be considered. (A bridge, on the other hand, mostly just stands there and lets things go over it.) For these reasons, I don't usually like this analogy.

Writing a book

In both cases, you're using text to build your deliverable. You have to break things into smaller pieces (classes, layers, etc. in software, chapters in books). You follow style guides, and have an ordering of things. All the little details you conjure up have to be consistent. In books, your characters should have past experiences that 'fit' in the context of the story. In programming, you need to make sure the data you need is available to all facets of the application that require it.

But.... I think writing a book is probably a lot less restrictive than programming. You have more freedom in the way you express things, for instance. (I don't think most editors are as picky as compilers.) In some ways, this makes programming easier-- once you have your goals defined, the ways you can go about achieving them are narrowed down. The degree of creativity is high in both cases.

Painting a picture

Painting a picture can be like programming because you're making something creatively, and you're building it in a sort of iterative manner. This is somewhat like the book argument, except the painting seems a little less constrained in places. You can choose your medium-- oil paint, water color, chalk, etc. much as you can choose your implementation language in programming. Programmers can also bootstrap projects by copying the work of others. ('Hello World', anyone? It can be seen sort of like paint-by-numbers.)

But.... paintings don't have to be exact. Their 'goodness' is found in the eye of the beholder. Oh, if only programs were that way!

Assembling a child's toy
Have you put together a bigger toy lately? They usually come in a cardboard box with about a hundred different parts in it, with an instruction sheet written in half a dozen languages. The assembler (you) reads the instructions and attaches part A to part B. The instructions (like documentation in software) are sometimes good, sometimes not. Sometimes you have to refer to a picture of the toy to see how to do it. This is like studying design patterns or reference implementations. In today's programming world, (especially Java) we have a lot of frameworks that make programming seem like this.

But... You never really fabricate anything by yourself in the toy scenario. You're using parts somebody else made. So I don't think this one is exactly right, either.

Those are some of the metaphors I've used. If you have any better ones, please share!

Happy Coding!


Anonymous said...


Anonymous said...

Here is another one:
Programming is like writing a play.
Testing is like rehearsing the play.
A program execution is like a performance of the play.

This theatre metaphor was first put forward by Kristen Nygaard, father of OOP. See

sam said...

The toy analogy is a good one, you can take the analogy further and assume we are dealing with lego blocks including functional parts like gears, pulleys, motors, battery, etc that we have to put together to perhaps solve certain problem. Child's play really.

Anonymous said...

I don't go for Feng Shui, but common perception of it might be fairly well aligned. You have a structure to follow, and rules, but the ability to be quite creative within those constraints. It can be applied to a variety of constructs - gardens, buildings, rooms. But in the end, there's a clear "wrong way" to do something that might be seen as a compiler analogy.

Will said...

I've always used the 'building a house' metaphor when dealing with bosses/clients to better stress why they can't go changing the scope halfway through a project, "You can't go pulling out walls or the roof will cave in".

Personally I like a 'sculpture' methaphor. You start with a blob of clay, (the idea) and you start refining (iterating) down to the final product. Like any great art you never really finish, you just stop.

Tom Chiverton said...

"never really fabricate anything by yourself in the toy scenario"

Unless you are hand toggling the input panel of a PDP 11 or something, you never really fabricate anything by yourself in the programing world either...

Anonymous said...

funny how no one came up with the "programming is like sex" metaphor...

Marko said...

The house / bridge analogy seems to be very good as both are not quite simple things to make.. but as you said once built the serve their purpose without any noticeable maintenance as we have here in software business (customer support anybody?). So better analogy might be something that requires maintenance, like an expensive car. You need to build it carefully, just for the right market and you need to maintain and tweak it when it's on the road.

Frank Silbermann said...

How about this:

Programming is like designing a factory. You have to think of all the things that need to be done, the order in which they need to be done, and the speed at which things need to be done. You have to lay things out so that operations that need to communicate and transfer work products have convenient access to each other. And you have to organize it so that production is easy to manager -- easy for higher-level managers to know what is going on at all times, easy to focus management's attention on the performance of one unit at a time, and easy to get at the machinery for repairs when installed machines prove defective. And you have to design it for ease of expansion when changes are made to the products you build.

The difference between programming and designing factories is that human operators play little if any role in the operations, and you rarely have to be concerned about things like climate control or power supply. And it's a lot cheaper to build prototypes and modify them, so you don't have to design everything all at once before you start building. When you're designing factories of information instead of factories of products, you have somewhat more freedom in your design process, but many similar problems nevertheless.

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Peter said...

Great analogy! I like the ones in the comments, too!
Recently I started posting interestnig analogies I found on the web on I thought it could be a good idea to create a place where people can share useful analogies such as yours.