Reviewer comments and final review (#1)

* 371: Clarify Monorepo

* 380 and 387 : Typos and section references

* 385: whitespace does not look nice

* 377: definition of OEM

* Fix autoformatter's whitespace madness

* 389: improve wording

* 390: font is Libertine in all figures

* ignore *.ts

* 393, 378, 381, 388, 389, 390, 379: worked further on findings (JM and KG)

* worked on references.bib

* 382: Reformulate sentence

* 383: express figure 2, get rid of some warnings.

* 384: devops handbook

* 376: short abstract

* 394: Scaling within introduction rephrased

* 396: feature model rephrased

* 386: refrase unit test demand paragraph

* 423: earlier intro of space and time dimension in variation

* 375: explain fear

* 395: restructure conclusion and focus on future work

* 375: Corrected typo

* 374: modularization

* Final review by Jochen and Karsten. DONE

Co-authored-by: Maletschek, Jochen (SD-RM) <[email protected]>

paper/.gitignore

@@ -1,10 +1,12 @@
 /texmfs
+/*.bak
 /*.aux
 /*.log
 /*.out
 /*.bbl
 /*.blg
 /*.fdb_latexmk
 /*.fls
+/*.ts
 /*.synctex.gz
 /paper.pdf

paper/challenge.tex

@@ -1,10 +1,10 @@
-\section{Challenge}
+\section{Challenge}\label{challenge}
 
-Our migration method is supposed to be a generic solution for a migration from a
-polyrepo project landscape to a monorepo SPL, but our circumstances might have
-some influence on the ideas that we share in this paper. This section will
-explain the challenges we had, both coming from the products' nature and its
-industry and also from our corporate processes and strategies.
+Our migration method is supposed to be a generic solution, but our company's
+circumstances might have some influence on the ideas that we share in this
+paper. This section will explain the challenges we had, both coming from the
+products' nature and its industry and also from our corporate processes and
+strategies.
 
 The projects that we migrated are in the area of electric cars for premium
 automobile manufacturers. The software is written in (Embedded) C and Matlab and
@@ -29,7 +29,7 @@ \section{Challenge}
 Dimensions repository. Dimensions is a Source Code Management (SCM) system
 similar to Revision Control System (RCS) used at the Marquardt GmbH for source
 code administration and project documentation. Each individual source code
-repository is a self-contained ready to build project, including all required
+repository is a self-contained ready-to-build project, including all required
 tools and libraries to build the product binaries, like compilers, MSYS and GNU
 Make. The C code was validated with Jenkins nightly builds. Those Jenkins
 scripts were located in separate repositories, not part of the project's
@@ -41,7 +41,7 @@ \section{Challenge}
 already existing project (`clone-and-own'). This approach had several benefits:
 the setup time was short and because a mature project was taken as basis, the
 project's software was stable already and debugging and adapting was possible.
-There was less work for generic parts and only hardware and customer specific
+There was less work for generic parts and only hardware and customer-specific
 modifications were required. However, this approach also caused a lot of
 disadvantages. By simply cloning an existing project there was not only a copy
 of functionality available in the new project, but also a copy of all its flaws.

paper/conclusion.tex

@@ -1,4 +1,4 @@
-\section{Conclusion and Future Work}
+\section{Conclusion and Future Work}\label{conclusion}
 
 This work provides an iterative and incremental migration strategy towards SPL
 for the software of a real-world product family of an automotive supplier. We
@@ -15,40 +15,40 @@ \section{Conclusion and Future Work}
   \item established a stable SPL with variants buildable at any time,
   \item reduced workload of developers by reducing the number of repositories,
   \item increased collaboration beyond project borders and
-  \item integrated all software sources of a product family into one git
+  \item integrated all software sources of a product family into one Git
         repository.
 \end{itemize}
 
-We implemented a build system with modern CMake fully supporting the concept of
-SPL variants.
-
 At the submission date's point of time we managed to proof about 50\% of our
-concept. The build system prototype required two persons full-time for six
-weeks, the implementation for migration step one and two required two persons
-full-time for three more months. Over a time frame of two months we
-incrementally added ten variants, while each import to the SPL was really fast
-due to the automated importing mechanism. We already started with
+concept. We implemented a build system with modern CMake fully supporting the
+concept of SPL variants. The build system prototype required two persons
+full-time for six weeks, the implementation for migration step one and two
+required two persons full-time for three more months. Over a time frame of two
+months we incrementally added ten variants, while each import to the SPL was
+really fast due to the automated importing mechanism. We already started with
 \textit{Modularization} of software components, but only converted a few
-components and begun with removing duplicates. Recently we focussed more on
+components and begun with removing duplicates. Recently we focused more on
 automation than on the SPL migration, as we saw more advantages there in the
 long run. The automation for CI/CD is helpful for the migration as well.
-Nevertheless, the build system requires some more features to be able to handle
-our migration step three and we plan to implement them in the coming months, in
-parallel to the \textit{Modularization} step of the software components.
 
-Additionally to the build system implementation and the actual migration of the
-embedded source code, it is required for us to qualify tools which have an
-impact on the created binaries or the processes to build them. This tool
+Nevertheless, the build system requires more features, e.g., a package manager
+for dependency handling and a unit test framework for Test Driven Development
+(TDD) to be able to support our migration steps two and three and we plan to
+implement them in the coming months, in parallel to the \textit{Modularization}
+of the software components. Additionally it is required to qualify tools which
+have an impact on the created binaries or the processes to build them. This tool
 qualification is requested by the ISO 26262 standard for safety reasons. We must
 take care that CMake, Ninja and KConfig are properly qualified. On the other
 hand, proprietary software might come with safety evaluations already. This
-should be kept in mind, when deciding for your tool landscape.
+should be kept in mind, when deciding for a future tool landscape.
 
 Besides all the discussed technical challenges, there were also social obstacles
-on the way to SPL. Fear was probably the strongest emotion we faced. At the
-beginning we were certain that all required build system features were
-implemented and we always had a backup plan to go back to the original
-repositories. There was no real threat and still no one had enough confidence to
-start the migration. Afterwards we do not see a reason for hesitation, but
+on the way to introduce an SPL.\@ Fear of change was probably the strongest
+emotion we faced. We feared the introduction of our SPL approach, although we
+were certain that all required build system features were implemented and we
+always had a backup plan to go back to the original repositories. On the other
+hand the development team had a lot of doubts to adapt fast enough to new tools
+and processes. There was no real threat and still no one had enough confidence
+to start the migration. Afterwards we do not see a reason for hesitation, but
 sometimes it simply needs someone brave in the team or someone pushing you. Our
 conclusion is: Just do it! And if you break it, make sure you can fix it fast!

paper/fonts/source.txt

@@ -0,0 +1 @@
+LateX class "acmart" uses font Libertine. Got it from here: https://libertine-fonts.org/

paper/images/step2-modularization-flow.drawio

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paper/introduction.tex

@@ -1,4 +1,4 @@
-\section{Introduction}
+\section{Introduction}\label{introduction}
 
 Development of product families rather than individual products is a goal for
 many engineering companies. Product Line Engineering (PLE) is a widely used
@@ -16,39 +16,40 @@ \section{Introduction}
 Lines (SPL)~\cite{confsplc2000}. An SPL increases reusability~\cite{Clem02a} and
 therefore increases quality and decreases development costs of software by
 building up shared core assets and customer-specific functionality. With this
-reuse in place, a business will be able to do larger scaling, with higher number
-of projects the development costs will drastically decrease compared to
-traditional engineering methods and the time-to-market will improve due to less
-development effort~\cite{confsplcAzanzaMD21}. Thus an SPL is one possible
-solution to win against competitors.
+reuse in place, a business will be able to do larger scaling. A higher number of
+projects will drastically decrease the development costs compared to traditional
+engineering methods and the time-to-market will improve due to less development
+effort~\cite{confsplcAzanzaMD21}. Thus an SPL is one possible solution to win
+against competitors.
 
 But even after years of research, source code migrations to SPL are still
 complicated and there are no bullet proof concepts available that are applicable
 to actively running projects with tight release plans. Much research has been
 done on product line architectures~\cite{Svahnberg1999EPLA,
-confsplcTomashchukLJ21} and system engineering \cite{confsplcSchaferBAKR21},
+confsplcTomashchukLJ21} and system engineering~\cite{confsplcSchaferBAKR21},
 about feature model migrations~\cite{ncstrlustuttgartfiINPROC200185,
 confsplcGrunerBKR20, confsplcDuszynskiDB19, confsplcFritschAR20}, SPL
 evolution~\cite{journalssmrQuintonVRBGS21, Svahnberg1999ESPL, Eise02b,
 kconfigKernel} and safety aspects~\cite{confsplcWolschke0SAM19} of SPLs. On the
-other hand, \cite{confoopslaHetrickKM06} and \cite{confsplcAbbasJLESS20} have
-written about the overall process, general benefits and a change of mindset,
-but not specifically about source code. Contrary to \cite{confsplcRubinCC13},
-cloned variants are no option for us anymore. The authors of
-\cite{Krueger2001SMC} reported different migration strategies more than 20 years
-ago already: (1) proactive, (2) extractive and (3) reactive, but no work
-described a mixture of extractive and reactive migrations, which we needed.
-Inspired by the work of \cite{confsplcJepsenDB07} we aim for a strategy with
-which we are able to migrate multiple repositories to a monorepo, allowing
-developers and software product managers to proceed with their own pace and
-according to the project plan without risking its deadlines and always being
-able to do a step backwards if neccessary.
+other hand, Hetrick et al.~\cite{confoopslaHetrickKM06} and Abbas et
+al.~\cite{confsplcAbbasJLESS20} have written about the overall process, general
+benefits and a change of mindset, but not specifically about source code.
+Contrary to Rubin et al.~\cite{confsplcRubinCC13}, cloned variants are no option
+for us anymore. Krueger~\cite{Krueger2001SMC} reported different migration
+strategies more than 20 years ago already: (1) proactive, (2) extractive and (3)
+reactive, but no work described a mixture of extractive and reactive migrations,
+which we need for existing and upcoming customer projects. Inspired by the work
+of Jepsen et al.~\cite{confsplcJepsenDB07} we aim for a strategy with which we
+are able to migrate multiple independent repositories to a scalable SPL,
+allowing developers and software product managers to proceed with their own pace
+and according to the project plan without risking its deadlines and always being
+able to do a step backwards if necessary.
 
 In this paper we propose an iterative and incremental migration strategy in
-three steps. We structured the paper in the following way: Section two stating
-the challenges we faced in our projects and industry to explain our view on the
-problem and why standard solutions did not work for us, section three explaining
-our three step solution of the source code migration in detail, presenting
-infrastructure and build system ideas and section four presenting our
-conclusion, an overview on where we stand right now and giving a forecast on
-future work.
+three steps. We structured the paper in the following way:
+Section~\ref{challenge} stating the challenges we faced in our projects and
+industry to explain our view on the problem and why standard solutions did not
+work for us, section~\ref{solution} explaining our three step solution of the
+source code migration in detail, presenting infrastructure and build system
+ideas and section~\ref{conclusion} presenting our conclusion, an overview on
+where we stand right now and giving a forecast on future work.