Re: [AM] The Spiral Model

Tom Gilb described Evloutionary development in 1985. That's the root of
the iterative/incremental approach to building software - prioritize,
build a little, evaluate with the customer.  This approach works toward
five of the twelve XP practices (Planning Process, Small Releases,
Refactoring, Customer On-Site, and Continuous Integration).

Barry Boehm presented the Spiral model in 1986 in ACM SIGSOFT Software
Engineering Notes and two years later in IEEE Computer.  It's
significantly different from XP: the iterations produce
"increasingly detailed elaborations of the system", where agile methods
try to produce increasingly complete systems. The Spiral Model applies
the same sequence of activities in each cycle: elaborate the objectives,
evaluate alternatives, elaborate the product definition, plan the next
round.  You don't typically start coding until the fourth or fifth
iteration - in the first iteration the "product definition" is
elaborated as requirements, in the second as analysis, in the third as
design, etc.  There is an explicit risk evaluation in each iteration,
with the possibility of stopping the project.  Once coding starts, the
iterations continue and do implement the system in an incremental,
iterative fashion.

Both Gilb and Boehm emphasize the importance of customer (and other
stakeholder) involvement throughout.

I think a lot of agilists would say that what they do actually maps well
to the Spiral model - that the first few elaborative cycles (the ones
preceding the start of coding) simply happen very rapidly and
informally, often in single meetings of all the stakeholders.

scott

| From: Barr Bill P<[email protected]>
| Date: Fri, 13 Feb 2004 08:42:09 -0500
| 
| 	This is a multipart message; text/plain parts are shown here;
| 	use ":" to see non-text parts.
| ----------------------------------------
| Part 1:
| Content-Type: text/plain
| 
| >If you take Spiral to the extreme that you build some new business
| functionality every few weeks, then you would be approaching agility.  This
| would end up forcing us to focus on only a few features.  The requirements, 
| 
| Doesn't this pretty much describe the RUP's implementation of the Spiral
| model?
| 
| For more information about AM, visit the Agile Modeling Home Page at www.agilemodeling.com
| 
| 
| ------_=_NextPart_001_01C3F236.FDC6B11E
| ----------------------------------------
| Part 2: text/html
| ----------------------------------------


-- 
scott preece
motorola urbana design center (il67), 1800 s. oak st., champaign, il  61820  
e-mail:	[email protected]	fax:	217-384-8550
phone:	217-384-8589	cell: 217-433-6114	pager: [email protected]

For more information about AM, visit the Agile Modeling Home Page at www.agilemodeling.com
--^----------------------------------------------------------------
This email was sent to: [email protected]

EASY UNSUBSCRIBE click here: http://topica.com/u/?bUrKDA.bWnbtk.Z2NtYS1h
Or send an email to: [email protected]

TOPICA - Start your own email discussion group. FREE!
http://www.topica.com/partner/tag02/create/index2.html
--^----------------------------------------------------------------