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RE: The Cost of Change Curve

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  • acockburn@aol.com
    In a message dated 4/1/2004 7:29:30 AM Mountain Standard Time, UncleBob writes:
    Message 1 of 115 , Apr 1, 2004
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      In a message dated 4/1/2004 7:29:30 AM Mountain Standard Time, UncleBob
      writes:
      <<Some folks have said that XP flattens the curve. I don't think that's true.
      I think that whatever flattening has taken place has been because of things
      that are outside of XP's control. I think XP works *because* of this
      flattening; I don't think XP causes the flattening.

      To be sure, the cost of change curve does reassert itself at some point --
      typically at or around deployment. Once you have deployed the software then
      fixing a bug and redeploying can be pretty expensive; though the factor or
      10,000 that Boehm measured thirty years ago is probably an exageration by
      todays standards.>>
      -->
      agreeing with and extending Bob's comments. I'm on record as saying that XP
      doesn't remove the exponential factor... and as Bob points out, deployment is
      the biggest jump. For those few organizations that have external test groups,
      that is the other big jump. Also, as Bob points out, much of the flattening
      that we discuss comes from improved development technology.

      Different from Bob and others, though I think people ought to _defend_ XP
      *using the exponential curve*. If XP lowers all the constants in the exponential
      curve, the cost savings are enormous. The result is that with XP the product
      is being shipped while with the older processes it was still in requirements
      analysis. Part of what we call flattening --- the fact that ideally a customer
      is within earshot --- is a matter of making the variables and constants very
      small. Part of what we call flattening --- the cost to add or change a new
      feature --- is a matter of working with simple designs and well-designed code.

      As far as I can tell, most of the exponential factors in the exponential
      curve centers around
      (a) communicating that there is something wrong, and
      (b) locating the place where that something needs altering.
      Which is why the transition to external test, and to deployment, causes the
      big jumps.
      The cost to actually make the change is not (possibly never was) the
      exponential factor.

      ==============================================
      Alistair Cockburn
      President, Humans and Technology

      http://alistair.cockburn.us alistair.cockburn@...
      1814 E. Fort Douglas Circle, Salt Lake City, UT 84103
      Phone: 801.582-3162 Fax: 775.416.6457

      Author of
      "Surviving Object-Oriented Projects" (1998)
      "Writing Effective Use Cases" (Jolt Productivity Award 2001)
      "Agile Software Development" (Jolt Productivity Award 2002)

      "La perfection est atteinte non quand il ne reste rien a ajouter,
      mais quand il ne reste rien a enlever." (Saint-Exupery)
      ==============================================


      [Non-text portions of this message have been removed]
    • Ron Jeffries
      ... No clue what you re referring to. I can search if you can give me more context ... Ron Jeffries www.XProgramming.com Those who attain to any excellence
      Message 115 of 115 , Apr 8, 2004
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        On Wednesday, April 7, 2004, at 9:55:42 PM, Kay Pentecost wrote:

        > I haven't gotten a really good answer yet... Except for some qualities that
        > Ron Jeffries listed a while ago... which provide a good starting point.
        > Maybe Ron would list them again. I have them printed out on several pieces
        > of paper so I come across them when I'm looking for something else... but I
        > don't know where they are now.

        No clue what you're referring to. I can search if you can give me more
        context ...

        Ron Jeffries
        www.XProgramming.com
        Those who attain to any excellence commonly spend life in some single
        pursuit, for excellence is not often gained upon easier terms.
        -- Samuel Johnson
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