Monday, July 21, 2008

Agile Bridge Analogy

It is quite common to make analogies between the IT industry and Civil engineering. Developers often compare software development and design with construction projects; for example, the importance of having a blueprint and following known successful practices. I have some hesitations about using analogies between these industries. I find the resources used by both industries fairly different and for that reason the analogies can create false expectations and reasoning. Nevertheless, I have been successfully using the analogy of building a bridge for explaining Agile development.

When I was a teenager, I spent my summer vacations in a small beach town near Rio de Janeiro. In that city (Rio das Ostras) there was a little river which separated two parts of the town. Back then there was no bridge to cross the river in a specific section of the town.

Over a few years, I was able to experience the bridge being built. When teaching Agile software development practices, I have been using the construction process for that bridge as an example of how Agile delivers business value incrementally and iteratively.

To better explain the analogy, I will take a look into the traditional approach for building bridges and then I will explain the Agile counterpart.

The Traditional development

Traditionally, a bridge construction will be planned in detail. The blueprint will be produced, the budget allocated and the schedule created (perhaps several months of construction).

'Big-bang release' is the term used to describe a common software development release. At the very end the software is released — one big (bang) release. But what happens if it is not successful?

Below are some photos from unfinished bridges.

Half-built bridges or long running construction does not deliver any business value: nobody is able to cross the river!

The Agile Development

Let’s now look into the Agile approach for building a bridge.

The figure below shows a first version view of the bridge (maybe after a first iteration). Even being very simple (and fast to plan and build) the bridge delivers business value: one person at a time can cross the river.

At the next iteration, another piece of wood is added to the bridge. Now, the bridge handles more load and two people can cross the bridge at a time, as well as bicycles and motorbikes.

Perhaps, for the next iteration(s), the bridge is reinforced and now people, bikes, motorbikes and light vehicles are able to cross the river.

Following an iterative and incremental development style, extra reinforcements are added to the bridge during the next iteration(s) and now people, bicycles, motorbikes, light and heavier vehicles can cross the river.

Even though it took a while to reach the current stage of the bridge, business value was delivered all along.

In this blog entry, I used an analogy between building bridges and developing software. I wrote about an Agile approach for building bridges. In fact, in this approach I have been a satisfied end user (someone wanting to cross a river). Furthermore, I used this analogy to illustrate how Agile focuses on delivering business value incrementally (and in shorter release cycles) through an iterative development process.

Even though in this example I compared software development to building a small bridge, Agile has been proven to work for large projects as well. I have witnessed large successful Agile projects for which business value was iteratively and incrementally delivered.


Unknown said...

Nice reading Paulo.

Mario León said...

Excellent analogy.

Max said...

Except each bridge was a complete recreation of the first!

DCB said...

And none of these bridges would actually support high volume traffic in a city such as New York.
Nor does it appear that this would work well over any large sized body of water.

In general this would work great for a small river with relatively little traffic.

Just like agile, getting it to work well with it works great for small groups, getting it to work in a large enterprise isn't quite the same thing :)

Ricky said...

nah man, i dont agree with this analogy at all. if i was an end user i'd be pretty annoyed.

like first i'd have to put up with a bare bone minimum implementation that's hard to use (balance on a log).

then i'd have to put up with sharing that log, until the next log is implemented. Which again is another bare bone implementation. (now there's more traffic too)

and repeat.

until we have cars travelling on an infrastructure never intended to be used this way.

that just sounds like windows.

Anonymous said...

Good analogy. The real reason for chossing Agile is to give constant business value.

It is true that it is a small town and the bridge doesn't serve good for cities like Newyork. Applying principles of Civil engineering in which all the projects are failure leads to loss of life to enterprise (not mission critical) software development where failure is not so serious may not be entirely apt.. But still the example is a good one.

Jon Strayer said...

Software isn't hardware. You don't have to recreate each iteration from scratch.

Inside every large project is a small project (or a set of small projects) struggling to get out.

No matter if you eventually want to drive across the bridge, being able to walk across today is valuable.

John said...

I love your analogy here... Perhaps you will enjoy my blog entry comparing the construction of a house with the implementation of a managed business process: The best way to build a house is the worst way to implement a process

Anonymous said...

We can't forget we've been building bridges for thousands of years. Software development is a less than 50 year old science. We still don't know exactly how to build software. Here's a reference:

Anonymous said...

At first glance I found the analogy was nice. It delivers the main message that is to start simple and add complexity afterward when you have a better knowledge of user needs, business opportunities and technical feasibility. But it turned out that there are more counter-analogies between the two industries. What's about building a big city bridge by starting with a piece of wood or changing its pillars after it starts being used.
It's difficult to compare an industry that produces real objects with an other one that produces only abstract artifacts. The latter has strong constraints and can only deliver one version to its customers. The former has more freedom and can deliver a weak "1.0" in most of the cases (not all of them).

Holger said...

I agree, it's a nice little example, at first glance but does not really work for following reason:
Besides typical constraints like difficult local facilities and logistics, minimized constraints to ongoing business, traffic, etc., civil engineering project often have to deal with high costs and limited time to delivery (of the complete scope!). Therefore, depending on the type of construction, I cannot believe that a customer will agree to a solution, that require more additional costs and time than necessary by providing intermediate solutions, that will be partly or completely removed for the next stage.
Thus the example shows mainly, that Agile is not the all purpose approach and applicable to all kinds or projects.

Jon Strayer said...

Guys, in the long run no analogy works.

He had an experience where he observed that building a bridge in an incremental fashion deliver value for the users fast than trying to build the final form would have.

That's what incremental development of software does.

That's all. Don't try to read several books worth of details into a simple analogy.

Jonathan Harley said...

I don't think it's a fair criticism to say you couldn't build a city bridge this way. You couldn't build it in an agile way, but the design of such a bridge takes many months and you could do that in an agile, iterative way, releasing your first drawings to the rest of the company straight away, and each later set of drawings as you refine the design. It doesn't deliver business value but it would certainly lower the risk that the finished bridge would fail to deliver business value.

Lots more thoughts about this on our blog at

Anonymous said...

Articles are meaningful, and your blog is nice!
polo jacket
polo shirt
ralp lauren jacket
cheap polo shirts
spyder jackets
discount polo shirts
ralph lauren shirt
columbia jacket
north face jacket
cheap ralph lauren shirts
women's columbia jackets
polo t shirts
polo men's shirt
ralph lauren men's shirt
polo mens shirt
cheap polo jackets
ralph lauren mens shirt
wholesale polo jacket
ralp lauren polo shirts
short sleeve polo shirt
men polo shirt
lacoste polo shirts
wholesale polo shirts
men's polo shirts
cheap polo ralph lauren
cheap polo t-shirts
cheap polo clothes
custom polo shirts
discount north face jackets
ladies spyder jacket
tennis rackets
tennis racket
tennis racquet
tennis racquets
wilson tennis rackets
prince tennis rackets
head tennis rackets
babolat tennis rackets
best tennis racket
cheap tennis rackets
wilson tennis racquets
head tennis racquets
babolat tennis racquets
cheap tennis racket

immwhim said...

Anton Bauer camcorder battery
Aztec camcorder battery
Bosch camcorder battery
Canon camcorder battery
Chinon camcorder battery
Duracell camcorder battery
Empire camcorder battery
Energizer camcorder battery
Hitachi camcorder battery
Idx camcorder battery
Ikegami camcorder battery
Jc Penney camcorder battery
Jvc camcorder battery
Magnavox camcorder battery
Medion camcorder battery
Minolta camcorder battery
Mitsubishi camcorder battery
Multi-fit(h) camcorder battery
Panasonic camcorder battery
Philips camcorder battery
Photoco camcorder battery
Quasar camcorder battery
Rca camcorder battery
Saft camcorder battery
Samsung camcorder battery
Sharp camcorder battery
Sony camcorder battery
Sylvania camcorder battery
Thomson camcorder battery
Thomson/philips camcorder battery
Toshiba camcorder battery
Two-ways camcorder battery
Zenith camcorder battery

Anonymous said...

Your blog is very good, it's the best blog I've ever seen, thank you!
By the way, do you like polo shirts, which are very chic, especially the polo t shirts, I love them very much. I also like playing tennis rackets, it can keep healthy, what do you like to do? I'd like to introduce myself as the outlet of polo t shirts women, polo t shirts on sale, and polo t shirts for women. These products are our masterpieces, such as polo shirts on sale, polo shirts men, men's polo shirt, men polo shirt, mens polo shirts, mens polo shirt, besides we also sell cheap polo shirts, discount polo shirts, men's polo shirts, women's polo shirts. We are also the outlet of, cheap tennis racket, discount tennis racket, we recommend prince tennis racquet, head tennis rackets, wilson tennis racket, babolat tennis racquet. And it is our great pleasure that you come to our store online!

Anonymous said...
This comment has been removed by the author.
Anonymous said...

The EVA outsoles current provides a great offer of traction and cushioning and stay obvious of any probabilities of strain inside the feet.Moncler Online one can stays apart from a great offer of discomfort even although placing on this sort of beautiful UGG boots.Ugg Boots Outlet UGG boots from Mezoboots.Ugg Outlet Store com are quite lightweight and so are designed of EVA/rubber.Uggs boots uk These UGG boots are built to ensure which they could possibly be used devoid of socks only. Our boots that take place to be designed of pure sheepskin are this sort of which they adjust by themselves according for the dimension by stretching the leather.Ugg Clearance Sale I do not experienced very much make any difference picking among several possibilities current inside the website.ugg outlet It's effortless to decide on the size, the colours as well as the design and design that you simply need within your UGG boots within your website.Ugg Boots Clearance Sale I acquired my pair of UGG boots within of 5 times of placing my purchase inside the internet website - The UGG boots that take place to be supplied inside the internet website are also not prized the sky.uggs clearance Most using the traditional assortment is supplied for much lower than hundred dollars.uggs clearance That is typically a wonderful bargain and I am preparing to purchase one more one. subsequent all, these quite brightness unwanted fat UGG boots can perform wonders to feet. blog.ugg boots usa. Ugg UK. Ugg Boots Outlet. ugg australia uk. Ugg Boots UK. Ugg Online Store

teragoldonlinefsbest said...

Anonymous said...

Uggs on clearance common, although seriously, it might be a little costly. Wherever can i discover cost-effective uggs clearance, exceptional top quality, along with will not hurt you wallet import merchandise Uggs nederland sites qualities in a portion with the price conventional stores. You can purchase many merchandise through the manner moncler apparel in our online shop, price cut grows to 70%. They offer Moncler jacket sites (including Moncler totes), jacket Moncler decrease apparel, Moncler Outlet Moncler, to name a couple of jobs. We can easily certainly not not allow in which in a hip period Moncler Vente Prive, looking great, distinctive along with classy has become the want most of the people. Most of us often want to exhibit the particular originality of your style by simply seeking one thing pleasant along with attractive. Wearing a new effectively made jacket which has a well-known brand name produced onto it can be certainly gonna travel nearly all of your own fellows to really like your own feeling of manner along with design. You’d be considerably more charming in comparison with prior to. Also, the particular jerkin must have the main benefit of keeping your body comfortable, Uggs clearance especially in a few cool places, in which bitterly cool winter season often delivers a lot problems towards the local people. Aside from, many Moncler outlet online apparel are usually good quality, so that it can keep people comfortable along with ensure that you’ll appreciate wonderful admiration along with understanding. This enables you to avoid through individuals usual types which you utilized to placed on while in just about every winter Moncler Online Shop season. And so, in 2010 you need to head to buy Moncler sale different things. Our own distinctive along with Uggs clearance stylish types surely healthy the existing trends along with meet Moncler Outlet Store manner requires.

Anonymous said...

uggs clearance
uggs clearance
`ugg boots outlet
uggs clearance
moncler online shop
uggs on clearance

UGG Outlet Store
Cheap Ugg UK
ugg australia uk
ugg coupon

Anonymous said...

Uggs Clearance
Ugg Boots Clearance

Consumer Advocate said...

I guess this just5 goes to show there are multiple paths to the same destination. In this case 2 different, and successful ways to build a bridge.

fix credit

Anonymous said...

What if someone you never met, you never saw, someone you never knew, was the only someone for you IMVU Credit? It is better to have love and lost than never to have loved at all IMVU Credits, I love you not because of who you are, but because of who I am when I am with you IMVU Credit.

love supra said...

Thanks. I always enjoy reading your posts - they are always humorous and intelligent.You can learn more:China tours | China tour packages | China travel packages