Teaching Software Product Lines: A Snapshot of Current Practices and Challenges

Teaching Software Product Lines
A Snapshot of Current Practices and Challenges

Presented at SIGCSE 2018
Repository: http://teaching.variability.io/
TOCE article: https://hal.inria.fr/hal-01522779
SPLTea workshops: http://spltea.irisa.fr
Education and SPL in the CfP of SPLC 2017 and 2018:
http://splc2018.net/call-for-papers/call-for-research-papers/

2018 | Acher, Lopez-Herrejon, Rabiser (TOCE article: SPL/variability and teaching) https://teaching.variability.io 3
(Software) Product Lines

2018 | Acher, Lopez-Herrejon, Rabiser (TOCE article: SPL/variability and teaching) https://teaching.variability.io
Vari-ability in Software
“Industrial reality shows […] the number of variation
points, variants […], and dependencies […] easily
reaches staggering levels [...] often resulting in a
situation in which no one […] has a comprehensive overview
of the available variability.”
•  impacts all phases of development
and organizational structures
•  affects not only code, but also
documentation, test cases, …
•  emergent or planned
•  results from diverse decisions
made to address requirements
4
(c) Charles Krueger, BigLever

3 ways to build a (software) product
Indepently
5
„Clone & Own“ „Shared“ (reusable) Assets
Software Product Lines

Product Configuration
Variability Modeling
Components
Domain-specific Languages
Generators
Preprocessors
Design Patterns
…

(credits: Thorsten Berger’s slide)

Or
Xor
Mandatory
Optional
not, and, or, implies
Variability Models (feature models)
Variants of code (e.g., Java ou C)
Variants of user interfaces
Variants of video sequences
Variants of models (e.g., UML or
SysML)
…

Software Product Line and Variability
well-established in research and industry
Body of knowledge growing
7
12th International Workshop on
Variability Modelling of Software-
Intensive Systems,

What about teaching and software
product line?
• Teach or perish! What’s the point of doing research in
this field if you’re unable to disseminate your results and train
the engineers of tomorrow?
•  Education has a key role to play in disseminating the SPL knowledge
•  Research can also benefit from teaching
• We knew there are many initiatives here and there but
unclear to find out eg:
•  what is the material available
•  what are the possible gaps and difficulties faced
•  what is needed by industry
• Teaching SPLs is challenging
•  Relatively young discipline
•  SPLE encompasses a variety of topics (SE, PL, AI)
8

In a nutshell, there is a central question
How to teach
software product
lines and
variability?
9

Research Method
Stakeholders of
Software Product
Line Teaching
Survey on Teaching
of Software
Product Lines
SPLTea Workshops on
Software Product
Lines and Teaching
Survey on Learning
about Software
Product Lines
Researchers Educators Practitioners Students
Our Initiatives
Analyses of the State of Practice
Curriculum (e.g., length of course, topics
covered, audience, …)
Material (e.g., textbooks, tools used, ...)
Experience Reports
Challenges
Recommendations
Suggestions to improve the practice
Key messages and concrete actions
Analyses and
Discussions
Our Results

#1 Survey on Teaching of
Software Product Lines

Survey Design
•  91 contacts
•  pool of SPL researchers we know
teach
•  search for SPL courses online
•  review SPLC and VaMoS papers
•  On-line questionnaire (
http://www.surveygizmo.com/
s3/1342346/Teaching-Software-
Product-Lines)
•  13 enumerative and 5 open
questions
•  Feedback by colleagues to refine
questionnaire
•  34 complete responses and 15
partial
•  Decision: only analyze complete
responses
12

Survey Results
Respondents and their institutions
•  34 responses from 13 countries
•  Avg. SPL experience 10yrs, avg. SPL teaching experience 6yrs
•  Half say their research exp. = their teaching exp.
•  Institutions
•  15 research-focused
•  9 teaching-focused (colleges)
•  7 have both focuses
•  3 industrial institutions
•  Departments
•  CS (13), SE (9), IT (2)
•  others (10) -- all CS-related
•  16 full and self-contained SPL courses
•  18 teach SPL topics as part of other courses
13
Austria, 2
Canada, 1
Colombia, 1
France, 2
Germany,
12
Israel, 2
Italy, 1
Japan, 1
Korea, Rep.
Of, 1
Spain, 3
Switzerland,
1
USA, 6
Portugal, 1

Survey Results
Literature used
• 28 respondents use these books
• 25 use research papers, selected based on personal
preferences
• 12 use case studies, e.g., by van der Linden et al. 2007;
BigLever; Renault, STAGO, LINUX, and SPLOT; and own
case studies
14
0
1
2
3
4
5
6
7
8
9
10
Apel et al.
2013
Clements
and
Northrop
2001
Czarnecki
and
Eisenecker
2000
Gomaa
2005
Pohl et al.
2005
van der
Linden et
al. 2007
Weiss and
Lai 1999

Survey Results
Tools used
SPL Tool used by
None 8
FeatureIDE 6
BigLever's GEARS 4
FeatureHouse 3
pure system's pure::variants 3
AHEAD 2
CIDE 2
CVL 2
Feature Modelling Plug-in (FMP) 2
DOPLER, EasyProducer, FaMa, Familiar, FeatureMapper, Munge,
SPLAR, SPLOT, VARIAMOS, Varmod
1
each
C++, Metaprogramming, Software Generators, Xtext, MPS 1
Different tools for creating feature diagrams and UML-based models 1
Feature modeling UML tools extended for SPL 1
Haskell-Embedded Variation DSL 1
Own research prototypes 1
15
also see the survey by Berger et al. VaMoS 2013

Survey Results
Length, audience
•  Most courses are held over a semester (26)
•  3 "on demand", 2 as week-long courses, quarter (1), 1-2 days
seminars (1), and with a flexible schedule (1)
•  Average course length 24 hours (min: 1h; max: 120h)
16
0
2
4
6
8
10
12
14
Only Undergrads
Only Grads
Only Industry
People
Undergrads and
Grads
Grads and Industry
people
Undergrads
students and
Industry people
Undergrads, Grads,
and Industry people

Survey Results
Practical time, SPL lifecycle coverage
•  Practical time/overall course time 65% in average
17
Topic

Department
CS SE OT
Total

Requirements engineering 7 4 12 23
Testing 3 1 4 8
Modelling 9 8 13 30
Implementation 9 8 8 25
Maintenance & Evolution 9 3 5 17
Reverse engineering & SPL Adoption 7 2 1 10
Processes 5 6 8 19
Other 5 2 3 10
CS: Computer Science, SE: Software Engineering, OT: Other departments

Survey Results
Challenges of teaching SPL
•  Lack of and availability of well-documented real-world examples and
case studies suitable for teaching (16)
•  Complexity of the subject and required background knowledge (9)
•  Lack of and availability of SPL tools (7)
•  Acceptance on the curriculum and opening the mind of students (4)
•  "Even software engineering can be hard to teach as developing
large-scale systems does not connect to students hands-on
experience of developing rather small solutions. Teaching SPL
means SE for many systems, this does even less relate to students'
experiences."
18

Survey Results
How to improve the state of teaching SPL
•  Improved textbook examples and case studies (13)
•  Better tools for students (7)
•  Broaden the focus of teaching SPLs (3)
•  SPL is already mainstream! (2)
•  Other ideas
•  videos of experts to motivate SPLs and explain key concepts and ideas
•  incorporate the notions and terminology of SPLs more in other courses
•  develop a standard curriculum and evaluation scheme for teaching SPLs
19

Survey Results
Impact of teaching SPL
•  On research
•  Student participation in research evaluations (11)
•  Finding research personnel (8)
•  Feedback on and discussion about tools, examples, case studies (6)
•  Connecting with industry (5)
•  Discussion of open research issues with students (2)
•  On practice
•  Teaching SPLE = preparation of introduction of SPLE in industry (13)
•  Makes students aware of the topic à students eventually end up in
industry or even are already working in industry à increases awareness of
SPL in industry and trains future practitioners (7)
•  Teaching SPLs can be the start of industry-academia collab. projects (2)
20

Survey Results
Other comments
•  Teaching SPLs together with model-driven development
•  very interesting from a teaching perspective
•  Having a common, clearly defined basis of terminology and concepts
taught at the majority of the institutions
•  would help a lot
•  Real-world SPLE is very different from research
•  Variability models seem to be the key topic in research
•  In practice it often is just one technique for some roles
•  Industry often successfully manages variability w/o dedicated models
•  Our survey was not a perfect fit for SPL consultants and trainers
•  True; we have to address this in our future work
•  Invite consultants/trainers in a workshop
21

#2 SPLTea Workshops 2014
and 2015

SPLTea’14: Experience Reports and
Industry Panelist
• 30+ attendees at SPLC 2014 (Florence, Italy)
• 3 experience reports
• Industry Panel
• Dr. Paul Clements, VP of customer success at BigLever
(a leading commercial SPL engineering tools provider)
• Dr. Martin Becker, head of Embedded Systems
Development at Fraunhofer IESE
• Dr. Steve Livengood, Software Architect at Samsung
Research America
• Dr. Juha Savolainen, (at that time) SW Director at
Danfoss Power Electronics

Industry Panel
24

Key points discussed at the
industry panel
• How should SPLs be taught so that students
going to industry have the required knowledge?
• SPL infuses additional complexity in the software
engineering problems – students should be aware of it.
• What is the required SPL knowledge for industry,
e.g., how relevant are variability models?
• treat variability in the same way as other basic
functional and non-functional properties are treated
• What are the challenges of teaching SPLs in the
light of the needs of the industry?
• “technology is easy, people are not”
25

Key points discussed at the
industry panel
• How can the state of teaching SPLs be improved?
• Making the courses more “realistic”
• Elevating variability as core concepts in standard SE curricula
• How could industry be better involved in teaching SPLs?
• Industry involvement in the teaching of SPLs should be seen as
a mutually beneficial activity
• Product line tools used in industry can/should be used
• Scenario: SPLs going mainstream?
• In the past, companies were unwilling to publicly acknowledge
their use of SPL. Now, they instead not only publicly
acknowledge their use but go as far as to advertise it.
Teaching can be a catalyst for this scenario to materialize.
26

Experience reports and insigths
• Variability in… teaching experiences:
•  Seidl and Domachowska presented their experiences on ’Teaching
Variability Engineering to Cognitive Psychologists’
•  McGregor reported about ’Ten Years of the Arcade Game Maker
Pedagogical Product Line’
•  Collet et al. presented their ’Experiences in Teaching Variability
Modeling and Model-driven Generative Techniques’
• Other discussions at the workshops
• Need for case studies
• Curriculum and different ways to teach SPL knowledge
• Populating a repository of teaching material
27

SPLTea’15 (Nashville, USA, SPLC 2015)
•  Brainstorming about a repository of teaching material for product
lines and variability
•  Questions like:
•  What could be the desirable features, services, and underlying technology
of such a repository? How to collect more resources (including slides,
lecture notes, lab instructions, tools)? How to involve industry? How to
advertise the existence of the repository?
•  For which: educators only? researchers? students? practitioners? both?
•  How to build a network of SPL educators?
•  How to make it possible for people to browse and understand the SPL
knowledge of the repository?
• Result and ongoing effort: http://teaching.variability.io
28

Survey on Learning About SPLs
•  What did you expect from this course before it started?
•  What did you actually learn from this course?
•  What did you not learn and/or would have wanted to hear
more about?
•  Please define in your own words what a Software Product
Line is.
•  What do you think is the most challenging part of learning
about Software Product Line?
• Suggestions to improve the state of the teaching of
Software Product Lines?
• How can the teaching of Software Product Lines impact
industrial practice?
• Any other comments
30

Courses and Countries
31

Students’ Expectations and Perceived
learning effects
• They expected to learn:
•  “managing a complex software system”
•  “more about product management and testing”
•  “handling the process of developing similar software”
•  “different approaches how SPLs could be implemented”
• They learned:
•  All students replied that they learned the basics of SPL engineering
and the involved processes (application and domain engineering)
•  Eight students replied that besides the basics and theory of SPLs
they also learned how to apply SPL engineering in practice based
on presented case studies and implementation examples
•  “I learned several approaches how SPLs could be implemented,
the advantages & disadvantages of them and got live experience
of how much programming effort each approach takes”
32

Missed student interests
• More practical examples and tools or more about
recent case studies or experience reports from SPLs
• They wanted but did not learn about the barriers for
adopting SPL concepts in a real software organization
and how to introduce the SPL culture in a company
• Would have wished for more links between model-
driven engineering and SPL engineering
• “SPL engineering often seems to be presented as a (too)
ideal approach to develop software but does not (enough)
take into account the reality that existing (legacy) software
still needs to be maintained and/or refactored into an SPL”
33

Challenges students perceive
• Seven students (all without industry job) think that “it is very
challenging to understand the general concept of (large-
scale) reuse as a student”
• Understanding the basic concepts of SPL engineering,
especially “imagining how it will work in practice is difficult”
• A lot of background knowledge is required to understand
SPLs, especially a lot of experience in software engineering
• Difficulties understanding “cross-cutting concerns” and
“feature interactions”
• Other challenges:
•  visualization of variability; understanding the mapping of abstract
features to concrete software artifacts
•  maintenance of the many variants created (derived) based on a
product line
34

Suggestions to improve teaching by
students
• Include more practical activities and discussions and details
on how to transfer the theoretical knowledge to the real world
(e.g., “providing detailed solutions to practical exercises”)
• Let students try out commercial SPL tools
• Compare SPL engineering with other recent approaches such
as agile development
• “It would be a good idea to work on one big, concrete project
throughout the semester to experience the development of a
SPL from scratch”
35

Wrap-up and Future
Stakeholders of
Software Product
Line Teaching
Survey on Teaching
of Software
Product Lines
SPLTea Workshops on
Software Product
Lines and Teaching
Survey on Learning
about Software
Product Lines
Researchers Educators Practitioners Students
Our Initiatives
Analyses of the State of Practice
Curriculum (e.g., length of course, topics
covered, audience, …)
Material (e.g., textbooks, tools used, ...)
Experience Reports
Challenges
Recommendations
Suggestions to improve the practice
Key messages and concrete actions
Analyses and
Discussions
Our Results

Recommendations (based on insights)
• Curriculum integration: many possible scenarios
•  The design of a full course is not the only option for educators. Another
realistic alternative is to teach about SPLs as part of existing courses.
•  Teach SPLs at the graduate levels
•  Towards a baseline curriculum and evaluation scheme; customizable!
• From exercises to case studies
•  Despite early efforts, encompassing all SPL activities within an unique
case study is an open and difficult challenge.
•  Therefore it is more realistic to only consider a subset of SPL activities
•  Tools are no longer a source of anxiety and an obstacle: educators
now have a collection of tools for modeling and implementing SPLs
• Innovate, take risks, possibly deviate from current
practices, and eventually report on failures or successes
http://teaching.variability.io
37

Wrap up
• Software product line (SPL) and variability engineering: well-
established in research and industry
• Teach or perish!
• How to teach SPL and variability?
•  Instance of a general problem faced by other specialized fields (e.g.,
software testing, model-driven engineering, software language engineering)
• Surveys and insights from researchers, industry, educators,
and students
Repository: http://teaching.variability.io/
TOCE article: https://hal.inria.fr/hal-01522779
SPLTea workshops: http://spltea.irisa.fr
Eduction and SPL in the CfP of SPLC:
http://splc2018.net/call-for-papers/call-for-research-papers/
38

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