%&tex
\chapter{Design Method Evaluation}
    \label{chap:reflection}

    \section{Elements of a Feature}
        During the course of this study, the concepts of specifications, components and functions are added to the design method.
        As explained in the background chapter, having an approach to determine specifications is a crucial concept of a design process.
        Because \ac{ridm} did not include such an approach, a \ac{se} approach was added.
        The aim of the \ac{se} approach is to deliver a set of features to be used in the \ac{ridm}.
        To be more specific, the set of features was expected to be the result of the feature definition step.
        Contrary to that expectation, multiple attempts for this step did not produce a satisfactory definition of features.
        As explained in \autoref{sec:case_featuredefinition}, there was a clear discrepancy between the expected and resulting features.
        It was expected to get features in the form of components that can be developed during the design process.
        However, the resulting features came off as functions of the system.
        In the end, a solution was found in the RobMoSys approach.
        Even though the RobMoSys approach was too comprehensive for this case study, it provided the basis for the split between functions and components.
        Furthermore, it resulted in the hierarchical structure of functions and sub-functions as shown in \autoref{fig:robmosys}.

        \begin{figure}
            \centering
            \includegraphics[width=85mm]{graphics/functional_relation.pdf}
            \caption{Relations and elements within a feature. \autocite{kordon_model-based_2007}}
            \label{fig:functional_relation}
        \end{figure}

        Creating a hierarchy for the functions and a separate set of components allowed for the continuation of the case study.
        There were still a number of challenges with this approach.
        For example, it was almost impossible to divide the specifications between components and functions.
        Furthermore, the roll of electronics did not fit in the current approach either.
        In reviewing the literature, the approach used in this case study shows clear resemblances with \ac{mbed} \autocite{kordon_model-based_2007}.
        \ac{mbed} introduces explicit relations between the requirements, components and functions, as shown in \autoref{fig:functional_relation}.
        Additionally, the paper includes a layout for the hierarchy of requirements, functions and components.
        Based on this, the approach by \textcite{kordon_model-based_2007} further supports the idea of dividing features into specifications or requirements, functions, and components.

        What is interesting about this new insight is that it helps to understand the difference with the case study performed by \textcite{broenink_rapid_2019}.
        The hardware components used by Broenink and Broenink was a mini-segway, which was designed for a student project.
        The requirement for this mini-segway to be able to balance, drive and steer, is inherited directly from the student project.
        Causing the requirements and components to be implicitly defined in their case study.
        Therefore, the function that needs to be implemented, fits very well within the definition of a feature.

    \section{Model and Design Relation}
        The \ac{ridm} as well as the design method in this study fail to make a explicit distinction between the model and the design.
        %Hierdoor wordt de harde grens hier tussen onduidelijk.
        This implicitly caused the model itself to dictate the design.
        %Een goed model voldoet namelijk aan het volgende ...
        According to \textcite{stachowiak_allgemeine_1973}, three general properties apply for a model.
        First is that the model is always representative to its original; 
        second, the model must only include attributes of its original that are relevant to the respective developer or user;
        and third, the model must be pragmatic to the original, meaning that models are an adaptation of the original with respect to a specific purpose.

        %Dus als je design verder ontwikkeld dan moet je dus schakelen tussen models.
        These properties coincide with the different modelling approaches used during the case study.
        The dynamic models did not start directly with 3D physics as it would conflict with the second property.
        However, as the design becomes more refined, it could not be represented with only basic kinematics calculations. 
        The step to 2D, and later 3D physics, is made such that the model still represents the design.
        Parallel to the dynamics model, a CAD drawing was used to model the shape of the hardware components.
        Simply because models represent the design for a different purpose.

        Even though the models in the case study satisfy the properties as described above, it has a significant implication for the current design method.
        As the model is used to represent the current design, switching to a different modelling approach changes the representation of the design as well.
        From the case study it is possible to identify two direct consequences.
        The first is that there is discrepancy for the required effort between a design change and the corresponding model update.
        This can be seen in the case study when the model was reconstructed with 3D physics but the design did not change.
        Resulting in a couple of days of work spend reconstructing the model, without significant progress in the design.
        The second consequence is that the design got split up over the dynamics model and the CAD drawing:
        Both included the kinematics of the SCARA;
        the controller and stepper behavior was defined in the dynamics model;
        and the shapes of the components was defined in the CAD drawing.
        Such a subdivision of details across different models is, without any doubt, undesired.


    \section{Information Flow}
        %% Aanknopen op het vorige verhaal?
        %Although team members improve the information flow within a design team, it does not guarantee that all information is available.
        %Throughout the case study, more and more information becomes available.
        %During the initial design, new insight was gained that would have been useful during the problem description and the specifications step.
        %And while making the tests, it became clear that the specifications were incomplete.
        %It is possible to review the specifications step, but the succeeding steps have to be redone as well. 
        %During the case study, I decided to continue with the design due to the scope of the research, namely the development design cycle was.

        %Dealing with these design changes is a known weakness of the waterfall model.
        %Many publications give credit to \textcite{royce_managing_1970}, for the concept of the waterfall model.
        %Where they refer to the simple 5 to 8 step design concept, similar to the one in \autoref{sec:SE}.
        %What these publications fail to address is that \textcite{royce_managing_1970} says: "I believe in this concept, but the implementation described above is risky and invites failure."
        %Followed by multiple steps of improving the waterfall model.
        %Royce adds a complete design step, loads of intermittent testing and documentation, and the instruction to "Do it twice".
        %On initial thought this feels as a disproportionate amount of extra work.
        %Especially since the current design plan already includes small feedback cycles.
        %However, the small feedback cycles only apply to the current design, and do not provide information about the current design direction.
        %Thus, the current level of detail might work, passing the tests of the current cycle does not guarantee a successful implementation of the design.
        %Based on the evaluation, it was often difficult to justify the design decisions as there was insufficient information.
        %A simple proof of concept would improve the information about the direction of the design, required resources and the feasibility of the project.
        %Although this requires additional work, it is very likely that it improves the projects feasibility and thus reducing the risks of the project.


