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Re: design practices

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  • Joel
    I have never managed a re-write project before, so perhaps my answer is naive, but here goes anyway. I disagree with some other respondents. I think that you
    Message 1 of 25 , Jan 4, 2005
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      I have never managed a re-write project before, so perhaps my answer
      is naive, but here goes anyway.
      I disagree with some other respondents. I think that you need to
      modify some Scrum/Agile practices because some assumptions are not
      valid in this type of project. For example, one assumption of Agile
      is that you should prioritize the functionality because lower
      priority functionality 1)might never be needed or 2)might not make
      economic sense by the time we get to it or 3) the user might just
      change their mind, (or other variations of this theme). One drawback
      of waterfall is that it treats all functionality with equal
      priority. But, in this case, all functionality may be required. The
      user may not want a replacement system unless it has ALL previous
      functionality, hence the need for prioritization assumption is no
      longer valid.
      Another assumption we frequently make is that design should be
      emergent. Writing code only for the current function is a good thing
      because re-writing isn't expensive compared to adding complexity and
      functionality that is never needed. But in the case where all
      functionality has equal priority, and the system cannot be released
      until all of the functionality is included, isn't this an inefficient
      approach?
      My guess is that this project would benefit from more up-front design
      than a new development project. And I think that I would be asking
      the team where else they can find efficiencies given the somewhat
      unique situation.

      --- In scrumdevelopment@yahoogroups.com, "Steven Mak" <tcmak@y...>
      wrote:
      >
      > Hi all,
      >
      > I am going to have a new project soon and I am the project manager
      of
      > the project. I want to apply scrum practices with this project. My
      > knowledge in scrum is limited to this group, some online materials,
      > and a book. Thus, hope this gives me practical experiences in how my
      > development team more 'agile'.
      >
      > The project is about re-writing a system that has been using for
      > serveral years. It's so badly written that it has to be re-written
      so
      > as to have a easier life to maintain it.
      >
      > The first query is not about 'design'. Is traditional software
      > development works better when we have deep understanding about the
      > system? (eg. re-writing a system that we have been using for
      serveral
      > years) or I would like to know how agile methologies work better in
      a
      > not-so-emergent system development.
      >
      > The scope of the system is rather board, thus I believe it would
      take
      > quite a number of iterations before its functionalities can compare
      > with the existing system.
      >
      > I am wondering, with such a large system. How infrastruture and
      > software design is done in Scrum, while not falling into the BDUF
      > problem? Suppose it's a 4-week iteration. Would 'design' and
      > 'architecutral' work takes up more time in the first few iterations
      > than the later iterations, as it gets sufficiently-built for most
      > services on top of it?
      >
      > Is there any references on recommended design practices in Scrum?
      > Thank you.
      >
      > Happy Holiday
      > Steven
    • Ron Jeffries
      ... I d wager a week s pay that for any proposed ALL previous functionality project, I can find at least one chunk of functionality that they don t really
      Message 2 of 25 , Jan 4, 2005
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        On Tuesday, January 4, 2005, at 10:30:01 PM, Joel wrote:

        > The
        > user may not want a replacement system unless it has ALL previous
        > functionality, hence the need for prioritization assumption is no
        > longer valid.

        I'd wager a week's pay that for any proposed "ALL previous
        functionality" project, I can find at least one chunk of
        functionality that they don't really want. Without mentioning price.
        If I can mention price, more.

        Ron Jeffries
        www.XProgramming.com
        What is your dream? And knowing this, what have you
        done to work towards realizing it today? -- Les Brown
      • Kristan Vingrys
        I think you missed one important point about the assumption of Agile and priority, The user might want the system before it is finished . In this case it
        Message 3 of 25 , Jan 4, 2005
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          I think you missed one important point about the assumption of Agile and priority, "The user might want the system before it is finished". In this case it would still be worthwhile prioritising the features to be implemented and working to that priority so if the user does come back before the system is finished they can make up there mind taking it as is knowing that the highest priority features have been implemented.
           
          With emergent design my understanding is that you should not make assumptions about features that maybe needed and design to those. In the case you are describing you know what features are required, therefore they should be considered in your design. In my opinion Agile practices do not discourage upfront design, they discourage making up features (but in the future they may want to ....).
           
          Regards,
           
          Kristan
          -----Original Message-----
          From: Joel [mailto:jadams@...]
          Sent: Wednesday, 5 January 2005 2:30 PM
          To: scrumdevelopment@yahoogroups.com
          Subject: [scrumdevelopment] Re: design practices


          I have never managed a re-write project before, so perhaps my answer
          is naive, but here goes anyway.
          I disagree with some other respondents.  I think that you need to
          modify some Scrum/Agile practices because some assumptions are not
          valid in this type of project.  For example, one assumption of Agile
          is that you should prioritize the functionality because lower
          priority functionality 1)might never be needed or 2)might not make
          economic sense by the time we get to it or 3) the user might just
          change their mind, (or other variations of this theme).  One drawback
          of waterfall is that it treats all functionality with equal
          priority.  But, in this case, all functionality may be required.  The
          user may not want a replacement system unless it has ALL previous
          functionality, hence the need for prioritization assumption is no
          longer valid. 
          Another assumption we frequently make is that design should be
          emergent.  Writing code only for the current function is a good thing
          because re-writing isn't expensive compared to adding complexity and
          functionality that is never needed.  But in the case where all
          functionality has equal priority, and the system cannot be released
          until all of the functionality is included, isn't this an inefficient
          approach?
          My guess is that this project would benefit from more up-front design
          than a new development project.  And I think that I would be asking
          the team where else they can find efficiencies given the somewhat
          unique situation.

          --- In scrumdevelopment@yahoogroups.com, "Steven Mak" <tcmak@y...>
          wrote:
          >
          > Hi all,
          >
          > I am going to have a new project soon and I am the project manager
          of
          > the project. I want to apply scrum practices with this project. My
          > knowledge in scrum is limited to this group, some online materials,
          > and a book. Thus, hope this gives me practical experiences in how my
          > development team more 'agile'.
          >
          > The project is about re-writing a system that has been using for
          > serveral years. It's so badly written that it has to be re-written
          so
          > as to have a easier life to maintain it.
          >
          > The first query is not about 'design'. Is traditional software
          > development works better when we have deep understanding about the
          > system? (eg. re-writing a system that we have been using for
          serveral
          > years) or I would like to know how agile methologies work better in
          a
          > not-so-emergent system development.
          >
          > The scope of the system is rather board, thus I believe it would
          take
          > quite a number of iterations before its functionalities can compare
          > with the existing system.
          >
          > I am wondering, with such a large system. How infrastruture and
          > software design is done in Scrum, while not falling into the BDUF
          > problem? Suppose it's a 4-week iteration. Would 'design' and
          > 'architecutral' work takes up more time in the first few iterations
          > than the later iterations, as it gets sufficiently-built for most
          > services on top of it?
          >
          > Is there any references on recommended design practices in Scrum?
          > Thank you.
          >
          > Happy Holiday
          > Steven





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        • woynam
          The key sentence is that all the functionality *may* be needed. I ve seen plenty of features that were never used, but they simply *had* to be there. Often,
          Message 4 of 25 , Jan 5, 2005
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            The key sentence is that all the functionality *may* be needed. I've
            seen plenty of features that were never used, but they simply *had* to
            be there. Often, there's no one who can tell you why a feature is
            needed, or why it was put there in the first place.

            I would start with the highest priority features first. At some point,
            the customer may decide that there's enough functionality to deploy
            into production. Worst case scenario, you rebuild all the features,
            which is basically were you might end up if you used a waterfall
            approach.

            Good case scenario, your customer decides that they can live with a
            subset of the features, and the system gets deployed into production
            eariler. You gain important feedback as you continue developing the
            remaining requested features.

            Best case scenario, the customer decides they *don't* need the
            remaining feqatures, but would rather you work on some *new* feature
            that will benefit the business. If you had taken the waterfall
            approach, your answer may be, "Sorry, we can't do that. We're 12
            months into a 18 month rewrite, and all we have is a bunch of design
            documents. We have to code and test the system first before we can
            begin to worry about changes." :-)

            Mark

            --- In scrumdevelopment@yahoogroups.com, "Joel" <jadams@d...> wrote:
            >
            > I have never managed a re-write project before, so perhaps my
            answer
            > is naive, but here goes anyway.
            > I disagree with some other respondents. I think that you need to
            > modify some Scrum/Agile practices because some assumptions are not
            > valid in this type of project. For example, one assumption of
            Agile
            > is that you should prioritize the functionality because lower
            > priority functionality 1)might never be needed or 2)might not make
            > economic sense by the time we get to it or 3) the user might just
            > change their mind, (or other variations of this theme). One
            drawback
            > of waterfall is that it treats all functionality with equal
            > priority. But, in this case, all functionality may be required.
            The
            > user may not want a replacement system unless it has ALL previous
            > functionality, hence the need for prioritization assumption is no
            > longer valid.
            > Another assumption we frequently make is that design should be
            > emergent. Writing code only for the current function is a good
            thing
            > because re-writing isn't expensive compared to adding complexity
            and
            > functionality that is never needed. But in the case where all
            > functionality has equal priority, and the system cannot be released
            > until all of the functionality is included, isn't this an
            inefficient
            > approach?
            > My guess is that this project would benefit from more up-front
            design
            > than a new development project. And I think that I would be asking
            > the team where else they can find efficiencies given the somewhat
            > unique situation.
            >
            > --- In scrumdevelopment@yahoogroups.com, "Steven Mak" <tcmak@y...>
            > wrote:
            > >
            > > Hi all,
            > >
            > > I am going to have a new project soon and I am the project
            manager
            > of
            > > the project. I want to apply scrum practices with this project. My
            > > knowledge in scrum is limited to this group, some online
            materials,
            > > and a book. Thus, hope this gives me practical experiences in how
            my
            > > development team more 'agile'.
            > >
            > > The project is about re-writing a system that has been using for
            > > serveral years. It's so badly written that it has to be
            re-written
            > so
            > > as to have a easier life to maintain it.
            > >
            > > The first query is not about 'design'. Is traditional software
            > > development works better when we have deep understanding about the
            > > system? (eg. re-writing a system that we have been using for
            > serveral
            > > years) or I would like to know how agile methologies work better
            in
            > a
            > > not-so-emergent system development.
            > >
            > > The scope of the system is rather board, thus I believe it would
            > take
            > > quite a number of iterations before its functionalities can
            compare
            > > with the existing system.
            > >
            > > I am wondering, with such a large system. How infrastruture and
            > > software design is done in Scrum, while not falling into the BDUF
            > > problem? Suppose it's a 4-week iteration. Would 'design' and
            > > 'architecutral' work takes up more time in the first few
            iterations
            > > than the later iterations, as it gets sufficiently-built for most
            > > services on top of it?
            > >
            > > Is there any references on recommended design practices in Scrum?
            > > Thank you.
            > >
            > > Happy Holiday
            > > Steven
          • woynam
            Just a little background on my experience with rewrites. I ve been at my current position for 7+ years, and joined the company to work on a rewrite of our
            Message 5 of 25 , Jan 5, 2005
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              'Just a little background on my experience with rewrites.

              I've been at my current position for 7+ years, and joined the company
              to work on a rewrite of our mainframe-based trading system that
              supported our open-outcry trading model.

              Less than a year into the project, the threat of fully electronic,
              screen-based trading became a reality with the announcement of the
              first new options exchange in 25 years, the ISE. We were soon directed
              to change gears and build a screen-based system.

              Shortly after completing and deploying version 1.0 of the system, the
              trading of single stock futures was authorized, and the fear was that
              a futures exchange could steal a lot of our business. Thus, we began
              developing a screen-based futures trading engine as part of a joint
              venture with 2 other exchanges. This new system was built using 90% of
              the major components of the new system.

              Shortly after completing and deploying the 2nd version of the system,
              the business decided that a hybrid trading model, combining the best
              of open-outcry and screen-based trading, would allow us to better
              compete with the fully electronic markets. Thus, we began working on a
              hybrid trading system that utilizes elements of the mainframe system,
              and well as our new trading platform. We deployed this version over a
              year ago.

              In a nutshell, the mainframe system is still there, and is used for a
              number of products that continue to trade open-outcry, as well as
              being part of the hybrid trading system. Had we focused exclusively on
              replicating the functionality of the original system, we would have
              built the wrong system, as the business did not stand still in the
              face of tough competition. Not only we some features not needed, they
              were completely eliminated with the new business model.

              By iteratively developing and deploying the system, we were able to
              deal with the unexpected course corrections that came our way.

              This is the ultimate value of agility.

              Mark


              --- In scrumdevelopment@yahoogroups.com, "woynam" <woyna@c...> wrote:
              >
              > The key sentence is that all the functionality *may* be needed. I've
              > seen plenty of features that were never used, but they simply *had* to
              > be there. Often, there's no one who can tell you why a feature is
              > needed, or why it was put there in the first place.
              >
              > I would start with the highest priority features first. At some point,
              > the customer may decide that there's enough functionality to deploy
              > into production. Worst case scenario, you rebuild all the features,
              > which is basically were you might end up if you used a waterfall
              > approach.
              >
              > Good case scenario, your customer decides that they can live with a
              > subset of the features, and the system gets deployed into production
              > eariler. You gain important feedback as you continue developing the
              > remaining requested features.
              >
              > Best case scenario, the customer decides they *don't* need the
              > remaining feqatures, but would rather you work on some *new* feature
              > that will benefit the business. If you had taken the waterfall
              > approach, your answer may be, "Sorry, we can't do that. We're 12
              > months into a 18 month rewrite, and all we have is a bunch of design
              > documents. We have to code and test the system first before we can
              > begin to worry about changes." :-)
              >
              > Mark
              >
              > --- In scrumdevelopment@yahoogroups.com, "Joel" <jadams@d...> wrote:
              > >
              > > I have never managed a re-write project before, so perhaps my
              > answer
              > > is naive, but here goes anyway.
              > > I disagree with some other respondents. I think that you need to
              > > modify some Scrum/Agile practices because some assumptions are not
              > > valid in this type of project. For example, one assumption of
              > Agile
              > > is that you should prioritize the functionality because lower
              > > priority functionality 1)might never be needed or 2)might not make
              > > economic sense by the time we get to it or 3) the user might just
              > > change their mind, (or other variations of this theme). One
              > drawback
              > > of waterfall is that it treats all functionality with equal
              > > priority. But, in this case, all functionality may be required.
              > The
              > > user may not want a replacement system unless it has ALL previous
              > > functionality, hence the need for prioritization assumption is no
              > > longer valid.
              > > Another assumption we frequently make is that design should be
              > > emergent. Writing code only for the current function is a good
              > thing
              > > because re-writing isn't expensive compared to adding complexity
              > and
              > > functionality that is never needed. But in the case where all
              > > functionality has equal priority, and the system cannot be released
              > > until all of the functionality is included, isn't this an
              > inefficient
              > > approach?
              > > My guess is that this project would benefit from more up-front
              > design
              > > than a new development project. And I think that I would be asking
              > > the team where else they can find efficiencies given the somewhat
              > > unique situation.
              > >
              > > --- In scrumdevelopment@yahoogroups.com, "Steven Mak" <tcmak@y...>
              > > wrote:
              > > >
              > > > Hi all,
              > > >
              > > > I am going to have a new project soon and I am the project
              > manager
              > > of
              > > > the project. I want to apply scrum practices with this project. My
              > > > knowledge in scrum is limited to this group, some online
              > materials,
              > > > and a book. Thus, hope this gives me practical experiences in how
              > my
              > > > development team more 'agile'.
              > > >
              > > > The project is about re-writing a system that has been using for
              > > > serveral years. It's so badly written that it has to be
              > re-written
              > > so
              > > > as to have a easier life to maintain it.
              > > >
              > > > The first query is not about 'design'. Is traditional software
              > > > development works better when we have deep understanding about the
              > > > system? (eg. re-writing a system that we have been using for
              > > serveral
              > > > years) or I would like to know how agile methologies work better
              > in
              > > a
              > > > not-so-emergent system development.
              > > >
              > > > The scope of the system is rather board, thus I believe it would
              > > take
              > > > quite a number of iterations before its functionalities can
              > compare
              > > > with the existing system.
              > > >
              > > > I am wondering, with such a large system. How infrastruture and
              > > > software design is done in Scrum, while not falling into the BDUF
              > > > problem? Suppose it's a 4-week iteration. Would 'design' and
              > > > 'architecutral' work takes up more time in the first few
              > iterations
              > > > than the later iterations, as it gets sufficiently-built for most
              > > > services on top of it?
              > > >
              > > > Is there any references on recommended design practices in Scrum?
              > > > Thank you.
              > > >
              > > > Happy Holiday
              > > > Steven
            • Steven Gordon
              Emergent design has other benefits over up-front design besides being able to handle changing/uncertain/emergent requirements: 1. Emergent designs force the
              Message 6 of 25 , Jan 5, 2005
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                Emergent design has other benefits over up-front design besides being able to handle changing/uncertain/emergent requirements:

                1. Emergent designs force the code to be easily changable, whereas top-down holistic design can easily create code that is monolithically dependent on the current design. Even if requirements never changed, implementing the system a few requirements at a time results in a system that will be battle tested at being able to accommodate additional requirements after deployment.

                2. Developers can learn something from the design and implementation of a few requirements that will improve the design and implementation of the remaining requirements, whereas if we design the whole thing before implementing any of it, we get no feedback on whether the overall design strategy is a good one.

                3. We can better estimate how long it will take to complete the project from the first month of design and implementation of a few requirements from beginning to end than from just a month of pure design.

                Steven Gordon

                http://sf.asu.edu/




                --- In scrumdevelopment@yahoogroups.com, "Joel" <jadams@d...> wrote:
                > Another assumption we frequently make is that design should be
                > emergent. Writing code only for the current function is a good
                thing
                > because re-writing isn't expensive compared to adding complexity
                and
                > functionality that is never needed. But in the case where all
                > functionality has equal priority, and the system cannot be released
                > until all of the functionality is included, isn't this an
                inefficient
                > approach?
                > My guess is that this project would benefit from more up-front
                design
                > than a new development project. And I think that I would be asking
                > the team where else they can find efficiencies given the somewhat
                > unique situation.
              • todd
                ... This is a bit of FUD. There s nothing in top down design that makes it any more monolithic or dependent or less changeable than any other design approach.
                Message 7 of 25 , Jan 5, 2005
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                  Steven Gordon wrote:

                  > Emergent design has other benefits over up-front design besides being
                  > able to handle changing/uncertain/emergent requirements:
                  >
                  > 1. Emergent designs force the code to be easily changable, whereas
                  > top-down holistic design can easily create code that is monolithically
                  > dependent on the current design. Even if requirements never changed,
                  > implementing the system a few requirements at a time results in a
                  > system that will be battle tested at being able to accommodate
                  > additional requirements after deployment.


                  This is a bit of FUD. There's nothing in top down design that makes it
                  any more monolithic or dependent or less changeable than any other
                  design approach. If you know how to design your code to be testable and
                  changeable then it will be. And it can be far easier to add in new
                  requirements, depending on the nature of the new requirements. If people
                  add useless over complicated code that doesn't work then that's there
                  own issue, it's not required by any design methodology that i know of.
                  Nor will any design methodology prevent someone from doing stupid stuff.
                • Steven Gordon
                  The argument that if you know what you are doing, you can create a perfectly good software using any methodology (or even no methodology) defeats anything we
                  Message 8 of 25 , Jan 5, 2005
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                    The argument that if you know what you are doing, you can create a perfectly good software using any methodology (or even no methodology) defeats anything we say here. Given the current state of software today, this is not a very realistic or productive argument.

                    It is common sense that a design that has had new requirements added to it dozens of times in a principled way can be more trusted to be able to accommodate new requirements of similar kinds than a design that has never had any new requirements added to it.

                    -----Original Message-----
                    From: todd [mailto:todd@...]
                    Sent: Wed 1/5/2005 10:53 AM
                    To: scrumdevelopment@yahoogroups.com
                    Cc:
                    Subject: Re: [scrumdevelopment] Re: design practices




                    Steven Gordon wrote:

                    > Emergent design has other benefits over up-front design besides being
                    > able to handle changing/uncertain/emergent requirements:
                    >
                    > 1. Emergent designs force the code to be easily changable, whereas
                    > top-down holistic design can easily create code that is monolithically
                    > dependent on the current design. Even if requirements never changed,
                    > implementing the system a few requirements at a time results in a
                    > system that will be battle tested at being able to accommodate
                    > additional requirements after deployment.


                    This is a bit of FUD. There's nothing in top down design that makes it
                    any more monolithic or dependent or less changeable than any other
                    design approach. If you know how to design your code to be testable and
                    changeable then it will be. And it can be far easier to add in new
                    requirements, depending on the nature of the new requirements. If people
                    add useless over complicated code that doesn't work then that's there
                    own issue, it's not required by any design methodology that i know of.
                    Nor will any design methodology prevent someone from doing stupid stuff.
                  • todd
                    ... It s productive and realistic because you can t overcome this lack by adding a methodology. So dinging one methodology in favor another isn t fair, imho.
                    Message 9 of 25 , Jan 5, 2005
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                      Steven Gordon wrote:

                      > The argument that if you know what you are doing, you can create a
                      > perfectly good software using any methodology (or even no methodology)
                      > defeats anything we say here.

                      It's productive and realistic because you can't overcome this lack by
                      adding a methodology. So dinging one methodology in favor another isn't
                      fair, imho.

                      >
                      > It is common sense that a design that has had new requirements added
                      > to it dozens of times in a principled way can be more trusted to be
                      > able to accommodate new requirements of similar kinds than a design
                      > that has never had any new requirements added to it.

                      The use of the word "principled" defeats anything we say here. Given
                      the current state of software today, this is not a very realistic or
                      productive argument. :-)
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