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RE: [XP] Physical System Analogy

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  • Arrizza, John
    ... Is there a correlation between probabilities of events and the locality of defects or of complex code?
    Message 1 of 25 , Jul 2, 2001
      > -----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 2 of 25 , Jul 2, 2001
        "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 3 of 25 , Jul 2, 2001
          > -----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 4 of 25 , Jul 2, 2001
            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 5 of 25 , Jul 2, 2001
              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@...
              >
              > 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.
              >
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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 6 of 25 , Jul 2, 2001
                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 7 of 25 , Jul 3, 2001
                  > -----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 8 of 25 , Jul 6, 2001
                    > -----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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