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Re: [XP] Physical System Analogy

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  • nevin@smalltalk.org
    ... saying ... your ... run-time ... (the ... program ... Ah, yes. You are right of course. The image approach used by Smalltalk often makes me forget this
    Message 1 of 25 , Jul 2, 2001
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      --- In extremeprogramming@y..., Ron Jeffries <ronjeffries@a...> wrote:
      > Responding to nevin@s... (02:50 PM 7/2/2001 +0000):
      > >So, Ron, is that a vote FOR or AGAINST SmallLint? Or, are you
      saying
      > >that you don't think SmallLint is a run-time tool for detecting
      > >unclear code?
      > >
      > >I'm confused.
      >
      > I like SmallLint. And it is not a run-time tool because it lints
      your
      > program while your program is not running. A profiler would be a
      run-time
      > tool, as it analyzes the performance of my program as it runs. Lint
      (the
      > original) runs on the source. SmallLint runs by reflection, but my
      program
      > is not executing when SmallLint analyzes it.
      >
      > Does that make sense?

      Ah, yes. You are right of course. The image approach used by
      Smalltalk often makes me forget this distinction. But you are right--
      the new code introduced into the image is not exercised by SmallLint.

      Nevin
    • Michael Schneider
      ... Ron, Very good question, I will do my best to answer it. Our code base has evolved over the last 20 years, it all tended to be developed with the best
      Message 2 of 25 , Jul 2, 2001
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        Ron Jeffries wrote:

        > Responding to Michael Schneider (02:22 PM 7/2/2001 -0400):
        >
        > >We use several axis of data to determine where refactoring dollars
        > >are spent. Note: you use different function/per axis depending
        > >on what your business goals are for the current release.
        >
        > It sure seems in your report that you must be doing refactoring in very big
        > chunks: you actually _schedule_ it.
        >
        > What might happen if you refactored all the time instead?

        Ron,

        Very good question, I will do my best to answer it.

        Our code base has evolved over the last 20 years, it all tended to be
        developed with the "best practice" of the day. Some areas are very
        cheap to maintain, so they don't appear on the cost radar for architecture.
        These portions of the code are mature feature wise, so you probably won't
        go into them for new projects.

        Other areas have a maintenance cost, but there is no new added functionality
        to go there, so that would be a candidate for a scheduled refactor.
        The maintenance resource model is high 'nuf to put together a hit squad
        for a couple of weeks, to do some refactoring. Again the reason for the
        scheduling is that the functionality is mature, it is the maintenance cost
        that drives it, not new functionality.

        S.W.A.G Warning!!!!!!!!!!!!!!!!!!

        If the data indicates that the team would spend more then 40-60% of their
        time refactoring the old system, rather than adding new functionality,
        then it may be a scheduled refactor (really swagging here :-{ )

        Other refactoring goes with new projects, this is not scheduled as a separate task,
        developers are in that code, so they can clean up things that get in their way.

        In project mode, refactoring is always a possibility at any time. The 5 axis
        give people a set of data points to help do estimation at the beginning of a project.

        The axis data is also useful to get metrics to justify 10 people refactoring
        for a major portion of the project.

        Again a VERY rough metric is that we try to keep legacy system refactoring
        below 40-60% for a scheduled project, it just wacks the velocity too much to be able to predict outcome for the new features.

        Not much of a science on that call, just a tradeoff between fixed release date, and
        fixed resource.

        One very important point, it is much harder to justify a refactoring project that
        a new functionality project, so it is very import to refactor as part of your
        project. I would not hope to be able to schedule a refactor for the project
        that I am working on this release, it is imperative to do it right the first time.


        I wish that I could give you more that S.W.A.G's but that is about all that I have
        right now,
        Mike


        >
        >
        > Ronald E Jeffries
        > http://www.XProgramming.com
        > http://www.objectmentor.com
        >
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      • Arrizza, John
        ... model) ... Using a coverage tool I assume. How did you come up with the axes?
        Message 3 of 25 , Jul 2, 2001
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          > -----Original Message-----
          > From: Michael Schneider [mailto:michael.schneider@...]
          > Here are the Axis that we are working with:
          >
          > 1) Design Goals of Architecture - what do you want your
          > architecture to look like
          >
          > 2) Actual Design of Architecture - What is the current structure (static
          model)
          >
          > 3) Binary Dependency Structure - who calls who, how many
          > times, (hot spot from a link dependency)
          >
          > 4) Compile Dependency Structure - To compile file X, how much
          > of the world to I have to compile
          >
          > 5) Run Time Path Data - We run system tests against the code
          > to find out which areas are exercised when user scenarios are executed
          Using a coverage tool I assume.

          How did you come up with the axes?
        • Arrizza, John
          ... Is there a correlation between probabilities of events and the locality of defects or of complex code?
          Message 4 of 25 , Jul 2, 2001
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            > -----Original Message-----
            > From: Hugo Garcia [mailto:xpjava@...]
            > Still a casual description but by measuring the
            > probrabilities of events you avoid the mechanistic
            > view of things.

            Is there a correlation between probabilities of events and the locality of
            defects or of complex code?
          • Michael Schneider
            ... Axis 1) Is the architecture design, It is basically a UML Diagram with tools to enforce package dependency. Robert Martin from Object Mentor helped us
            Message 5 of 25 , Jul 2, 2001
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              "Arrizza, John" wrote:

              > > -----Original Message-----
              > > From: Michael Schneider [mailto:michael.schneider@...]
              > > Here are the Axis that we are working with:
              > >
              > > 1) Design Goals of Architecture - what do you want your
              > > architecture to look like
              > >
              > > 2) Actual Design of Architecture - What is the current structure (static
              > model)
              > >
              > > 3) Binary Dependency Structure - who calls who, how many
              > > times, (hot spot from a link dependency)
              > >
              > > 4) Compile Dependency Structure - To compile file X, how much
              > > of the world to I have to compile
              > >
              > > 5) Run Time Path Data - We run system tests against the code
              > > to find out which areas are exercised when user scenarios are executed
              > Using a coverage tool I assume.
              >
              > How did you come up with the axes?

              Axis 1) Is the architecture design, It is basically a UML Diagram with tools to
              enforce package dependency. Robert Martin from Object Mentor helped us
              with the techniques for Axis 1)

              Axis 2) This axis came from the impact of our legacy system on the new design,
              we would come up with great designs for Axis 1, but when you came to realize
              them in the context of the system, you were challenged. Axis 2 was a short cut
              to allows have everybody that knew how that old system "really-worked"
              in one room. By automating this, and visualizing it, the architecture could
              review the "as-is" and say Whoah There!!!, that is not quite right. It is the
              big picture tool of the architecture

              Axis 3) This was gleaned from the exe's and the library archives, it was the
              call tree, for each exe

              Axis 4) came from #include info, our tools group has been gather this info for
              ~8 years, we just had to mine what they already had, source navigator is
              a nice Free tool to get this kind of information

              Axis 5) This came from our system test data, this is data contributed by customers,
              and defects over time. This also has beta test ...... This is to try to get as close to a
              "customer-oriented" view as possible.

              The data from the 5 axis are relatively easy to get, the hard part was visualization,
              and axis relationships. graphVis and java3d can help with this.

              This approach seems to hold up, it is the relationship between the axis that
              we are working on most now.

              It is just 5 different meta-models of the architecture, no one is perfect, but
              together, they can give you good info on the state of your system.

              Don't rely on it to heavily though, it just give you approximate state
              of the system. Number can lull you into a false sense of security,
              or a false panic.

              Hope this helps,
              Mike


              >
              >
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            • Arrizza, John
              ... Actually, I meant why those axes and not some other set? John
              Message 6 of 25 , Jul 2, 2001
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                > -----Original Message-----
                > From: Michael Schneider [mailto:michael.schneider@...]
                > > How did you come up with the axes?
                >
                > Axis 1) Is the architecture design, It is basically a UML
                <snip>

                Actually, I meant why those axes and not some other set?
                John
              • Ron Jeffries
                ... The word legacy would have answered my question simply but without deep understanding of what you do. Your detailed remarks are very helpful. Thanks!
                Message 7 of 25 , Jul 2, 2001
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                  Responding to Michael Schneider (03:37 PM 7/2/2001 -0400):

                  >Very good question, I will do my best to answer it.
                  >
                  >Our code base has evolved over the last 20 years ...

                  The word "legacy" would have answered my question simply but without deep
                  understanding of what you do. Your detailed remarks are very helpful. Thanks!



                  Ronald E Jeffries
                  http://www.XProgramming.com
                  http://www.objectmentor.com
                • Michael Schneider
                  John, Those were developed over time to meet business/technical needs. We looked at the problems that we were facing, looked at the work others were doing,
                  Message 8 of 25 , Jul 2, 2001
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                    John,

                    Those were developed over time to meet business/technical needs.
                    We looked at the problems that we were facing, looked at the work
                    others were doing, then tried several things over time.

                    We picked axis that had some overlap, but gave a look at the architecture
                    from a different view. The overlap allowed relationships to be established,
                    the differences allowed views that were not possible without the
                    axis.

                    You may be able to get similar info from different axis, this set seems
                    to work well for us so far. Next year it may be the 7 axis, or we may
                    figured out how to merge 2 into 1 and then it would be the 4 axis.

                    With the relationships that we have now, it takes 5.

                    Hope this helps,
                    Mike



                    "Arrizza, John" wrote:

                    > > -----Original Message-----
                    > > From: Michael Schneider [mailto:michael.schneider@...]
                    > > > How did you come up with the axes?
                    > >
                    > > Axis 1) Is the architecture design, It is basically a UML
                    > <snip>
                    >
                    > Actually, I meant why those axes and not some other set?
                    > John
                    >
                    > To Post a message, send it to: extremeprogramming@...
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                    > To Unsubscribe, send a blank message to: extremeprogramming-unsubscribe@...
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                  • Hugo Garcia
                    Hmmmmm...... Good question. I will have to ponder for a while. -H ... __________________________________________________ Do You Yahoo!? Get personalized email
                    Message 9 of 25 , Jul 2, 2001
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                      Hmmmmm......

                      Good question. I will have to ponder for a while.

                      -H



                      --- "Arrizza, John" <john.arrizza@...> wrote:
                      > > -----Original Message-----
                      > > From: Hugo Garcia [mailto:xpjava@...]
                      > > Still a casual description but by measuring the
                      > > probrabilities of events you avoid the mechanistic
                      > > view of things.
                      >
                      > Is there a correlation between probabilities of
                      > events and the locality of
                      > defects or of complex code?
                      >
                      > To Post a message, send it to:
                      > extremeprogramming@...
                      >
                      > To Unsubscribe, send a blank message to:
                      > extremeprogramming-unsubscribe@...
                      >
                      > Don't miss XP UNIVERSE, the first US conference on
                      > XP and Agile Methods. see www.xpuniverse.com for
                      > details and registration.
                      >
                      > Your use of Yahoo! Groups is subject to
                      > http://docs.yahoo.com/info/terms/
                      >
                      >


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                    • Arrizza, John
                      ... I couldn t help but notice the similarity of the axes you chose to Lakos s recommendations in Large Scale C++ Development.
                      Message 10 of 25 , Jul 3, 2001
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                        > -----Original Message-----
                        > From: Michael Schneider [mailto:michael.schneider@...]
                        > Those were developed over time to meet business/technical needs.

                        I couldn't help but notice the similarity of the axes you chose to Lakos's
                        recommendations in Large Scale C++ Development.
                      • Arrizza, John
                        ... Just a thought: If the probability of an event is high then the likelihood of a defect is low. In other words, if an event occurs a lot then defects, if
                        Message 11 of 25 , Jul 6, 2001
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                          > -----Original Message-----
                          > From: Hugo Garcia [mailto:xpjava@...]
                          > Good question. I will have to ponder for a while.
                          > --- "Arrizza, John" <john.arrizza@...> wrote:
                          > > > -----Original Message-----
                          > > > From: Hugo Garcia [mailto:xpjava@...]
                          > > > Still a casual description but by measuring the
                          > > > probrabilities of events you avoid the mechanistic
                          > > > view of things.
                          > >
                          > > Is there a correlation between probabilities of
                          > > events and the locality of defects or of complex code?

                          Just a thought: If the probability of an event is high then the likelihood
                          of a defect is low. In other words, if an event occurs a lot then defects,
                          if any, will manifest themselves more often therefore they tend to get
                          fixed. (This also seems to jive with my experience.)

                          In a sense, this is one of the reasons behind Unit Testing. It causes events
                          to occur with (almost) even probability.

                          back to legacy systems:
                          On first blush, this implies that the first Unit Tests should be written for
                          the least used code. But perhaps there is low-use code and then there is
                          low-use code. An example of the latter is dead code. No point in unit
                          testing that. Ditto but less so for code that implements low priority/low
                          use features.

                          So what's left? Code that implements high-use features but is invoked "once
                          in a while".

                          And that implies this snippet:
                          1) Identify and remove all dead code by running a line coverage tool while
                          running the system over all features.
                          2) Identify code implementing high-use features by running a line coverage
                          tool while those features are run.
                          3) Write Unit Tests for the remaining code in all of the classes identified
                          in step1.

                          let me know what you think...
                          John
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