TOPIC: Iterative Vs Incremental project life cycles

Hi all,
I am struggling to understand what difference there is between iterative vs incremental life cycles.
As far as I understood, both life cycles add extra functionality in iterations. It is mentioned that incremental life cycles deliver the final product after the final iteration only.
Does this mean that the customer won't be able to use the product until the last iteration is over and the project is closed?
Does this mean that in the iterative life cycle, the product is finalized and put to the market as early as possible and then features get added to it in an iterative way?

Thank you in advance,
Tahar

Tahar,

The main difference between them is that an iterative process makes progress through continuous refinement while an incremental process makes progress through small increments. So if I am a PM for a software project, an iterative approach would be to initially build the overall product and then refine the weak areas, while an incremental approach would be to build each individual area one at a time.

Generally, an iterative product will get to market before an incremental product, but the incremental product will be more complete when initially released.

- Steven

Hi Steven,
Thanks a lot for the quick follow up, highly appreciated.
From the description you've given below, it sounds like iterative development is purely horizontal where one builds the full "unfinished" products while incremental focuses on building an shipping finished verticals of the product.

Again, thanks a lot for the quick follow up.

Kind regards,
Tahar

Tahar,

Steven sums it up well. An example of an incremental life cycle is developing a fully functional website. There's a new functionality being added to the website for each iteration, but the full website is delivered to the customer at the end of the project. As for iterative life cycle, think of a demo, a prototype of that website that you build and let the customer decide to proceed with the full-blown product.

Luke

Based on the response shared by Steven, I would further like to know that in incremental life cycle , the entire scope at higher level is known during the initiation stage or only part of the scope is known to develop the product incrementally by using series of iterations ?

To my best of understanding,In iterative LC , approach, entire scope at higher level is known during initiation of the project. Subsequently product development takes place through progressive elaboration.

Please clarify .

Thanks for the question Tahar and thank you Steven and Luke for the great answers! Let the studying continue!

can you please give an example , since i didn't understand what is mean at higher level ?
thanks

Steven,

Your following statement contradicts the APG, page 21:
"Generally, an iterative product will get to market before an incremental product, but the incremental product will be more complete when initially released."

In APG, p21, its mentioned that one of the characteristic of iterative life cycles is that they may take longer because they are optimized for learning rather than speed of delivery.

On p23 of AOG, its stated that:
"Incremental lifecycles optimize work for delivering value to sponsors or customers more often than a single, final product."
Hence we can conclude that Iterative Lifecycles take longer time than Incremental Lifecycles to deliver business value.

In my humble opinion, Iterative Life cycles don't deliver the product until the life cycle ends, but while the product (or a service) that's being developed, there could be multiple cycles of lets say "Analyze and Build" that the project would go thru to incorporate the customer feedback via prototype. The product however will be "delivered" at the end of the Iterative Lifecycle.

In Incremental Life Cycles, the value is delivered almost at the end of each cycle (iteration/sprint) and the customers/sponsors don't have to wait until the end of the project life cycle to receive the business value. In case of building a website, the team can deliver MVPs features (in the form of initial product) in earlier sprints, Sponsors/customers release the product with minimal features to their customers to start getting the business value. The development team continues adding additional features in subsequent releases until the Sponsor thinks that the product has achieved all the desired features.

Hi Steven,
Clear with your explanation. But I wish to confirm is incremental Lifecycle is a time boxed activity as similar to Iteration Lifecycle.

Thanks in Advance
L. KATHIRESAN

Steven Mudrinich, PMP wrote: Tahar,

The main difference between them is that an iterative process makes progress through continuous refinement while an incremental process makes progress through small increments. So if I am a PM for a software project, an iterative approach would be to initially build the overall product and then refine the weak areas, while an incremental approach would be to build each individual area one at a time.

Generally, an iterative product will get to market before an incremental product, but the incremental product will be more complete when initially released.

- Steven

Hey guys,

Did we find a difference between iterative vs incremental that sticks? I saw Steven's reply but I also saw that someone contradicted Steven's statements.

What did we decide on?

Very Nice Example

Thanks a lot

Excuse me, guys
Can you explain then the difference between agile and incremental LC approach?
I suppose both of them are based on stages both require feedback? or am I missing the point?
thanks a lot

While studying for the exam, I've been befuddle by Iterative vs Incremental.

Here's my take.
Iterative: Dress is done/sewn. Lower or shorten hem, Add/remove collar.

Incremental: Sew bodice of dress, attach skirt to bodice, hem skirt.

Please critique my answer.
Thank you

The best representation is the Figure 2-8 of the PMBOK 7
Both Iterative and Incremental are divided in steps, so in each step you need a feedback and adapt the next steps. However the philosophy is different:

- Iterative: try different ideas to clarify the final scope. For instance the scope is to go faster from one city to another. You can build running shoes, then a bike, then a motorbike, then a car. You add features, but still you can provide multiple deliverables

- Incremental: you progressively develop the scope. So if the scope is to build a car, you can have incremental steps of building the wheels, the engine, the brakes, the chassis, but you have 1 deliverable only at the end, which is the final car