This is my third in a series of 4 lectures on the topic of Evolving Software Ecosystems, presented during the NATO Marktoberdorf 2014 Summer School on Dependable Software System Engineering in Germany, August 2014.

1. Evolving6So9ware6Ecosystems6
Marktoberdorf6Summer6School62014
Lecture63
Tom6Mens6
So#ware(Engineering(Lab(
University(of(Mons
informa7que.umons.ac.be/genlog

2. Natural(Ecosystems

3. 65
Standing(on(the(shoulders(of(giants
Lamarck
Lotka
Volterra
Darwin
Pareto

4. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering
Main(Research(Ques7ons
Which(control(mechanisms(driving(
natural(ecosystems(can(be(used(to(
explain(dynamics(of(so#ware(
ecosystems?(
!
Which(mechanisms(and(measures(can(
we(borrow(from(ecology(to(explain(and(
predict(how(so#ware(projects(evolve?
66

5. Biological(evolu7on
AND(BY(A(
DUMMY

6. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 68
Terminology
Biological(ecosystem
Defini7ons
• Ecology:(the/scien$fic/study/of/
the/interac$ons/that/
determine/the/distribu$on/and/
abundance/of/organisms(
• Ecosystem:/the/physical/and/
biological/components/of/an/
environment/considered/in/
rela$on/to/each/other/as/a/unit/
– combines(all(living(
organisms((plants,(
animals,(micro?organisms)(
and(physical(components(
(light,(water,(soil,(rocks,(
minerals)
Example:(coral(reefs
• High(biodiversity:(polyps,(sea(
anemones,(fish,(mollusks,(
sponges,(algae

7. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 69
Comparison

8. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 70
Comparison
Two/dual/views

9. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 71
Comparison
software ecosystem - view 1
shared
libraries
environment: hardware, OS,
external software, developers,
users, ...
species
active projects
archived
projects
Two/dual/views

10. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 72
Comparison
Two/dual/views
software ecosystem - view 2
developers
environment: source code, tests,
commits, bug reports,
species
testers
end-users debuggers

11. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering
Comparison(
Bipar7te(networks
In(ecology(
hosts(?(parasites(
plants(?(pollinators
73
Periodic report - scientific results
Figure 3.3: Example of bi-partite mutualistic relationship
Mutual(dependency(and(
func7onal(redundancy:(
disappearance(of(one(species(
may(be(compensated(by(
other(species(
if(there(is(sufficient(diversity(
in(both(layers

12. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering
Comparison(
Bipar7te(networks
In(so#ware(ecosystems(
contributors(?(projects
74
Projet 1
Projet 2
Projet 3
Periodic report - scientific results
Figure 3.3: Example of bi-partite mutualistic relationship

13. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering
Comparison(
Bipar7te(networks
In(so#ware(ecosystems(
contributors(?(projects
75
Projet 1
Projet 2
Projet 3
Mutual(dependency(and(
func7onal(redundancy:(
disappearance(of(projects(or(
contributors(may(be(
compensated(by(others

14. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering
Ecological(theories(of
evolu7on(of(species
• Different(evolu7onary(theories(
• Natural(selec7on((Darwinism)(
• Re7culate(evolu7on(
• Hologenome(theory((symbiosis)
76

15. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 77
Evolu7onary(theories(
Darwinism
• all(species(of(life(have(
descended(over(7me(from(
common(ancestors(
• this(branching(patern(of(
evolu7on(resulted(from(natural6
selec&on,(similar(to(ar7ficial(
selec7on(in(selec7ve(breeding(
!
• Example(
– 13(types(of(Galapagos(finches,(
same(habits(and(characteris7cs,(
but(different(beaks
Charles(Darwin
(1809–1882)

16. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 78
Evolu7onary(theories(
Darwinism
Darwin((1837)• Evolu7on(history(of(species(can(be(
represented(by(a(phylogene/c$tree.(
• Describes(the(evolu7onary(
rela7onships(among(species(
assuming(that(they(share(a
common(ancestor.

17. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 79
Evolu7on(History
So#ware
• Type(to(enter(text

18. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 80
Evolu7onary(theories(
Re7culate(evolu7on
Re7culate(evolu7on(
• Evolu7on(history(is(represented(as(a
graph(structure(
!
• Two(or(more(evolu7onary(lineages(can(be
recombined(at(some(level(
• hybrid/specia$on
(2(lineages(recombine(to(create(a(new(one)((
• horizontal/gene/transfer
(genes(are(transferred(across(species)

19. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 81
Evolu7onary(theories(
Re7culate(evolu7on
Re7culate(evolu7on(of(so#ware(?(
((
• hybrid/specia$on
Distributed(version(control(systems((e.g.(Git)(promote(
re7culate(evolu7on(through(fork(and(merge(
In(prac7ce,(few(projects(actually(merge(
Robles/et/al./A/Comprehensive/Study/of/SoCware/Forks:/
Dates,/Reasons/and/Outcomes./OSS/Conference/2012,/
Best/Paper/Award.

20. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 82
Evolu7onary(theories(
Re7culate(evolu7on
Re7culate(evolu7on(of(so#ware(?((
!
• horizontal/gene/transfer
Transfer/of/technical/resources/(code)/
All(large(so#ware((eco)systems(exhibit((a(large(number(of(
accidental(or(deliberate(“code(clones”(and(“code(reuse”(
Very(ac7ve(research(domain(in(so#ware(engineering(
Mojica et al. “A Large Scale Empirical Study on
Software Reuse in Mobile Apps”; IEEE Software 2014

21. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 83
Evolu7onary(theories(
Re7culate(evolu7on
Re7culate(evolu7on(of(so#ware(?((
!
• horizontal/gene/transfer
Transfer/of/human/resources/
How/do/project/contributors/join,/leave/and/move/across/
projects/in/the/ecosystem?/
How/are/newcomers/aQracted/to/an/ecosystem?
Weiss(et(al.(Evolu$on/of/Open/Source/Communi$es./OSS(2006(
Bird(et(al.(Open/Borders?/Immigra$on/in/Open/Source/Projects./MSR(2007(
Jergensen(et(al.(The/onion/patch:/migra$on/in/open/source/ecosystems./ESEC/FSE(2011(
Canfora(et(al.(Who/is/going/to/mentor/newcomers/in/open/source/projects?(FSE(2012

22. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 84
Evolu7onary(theories(
Re7culate(evolu7on

23. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 85
Evolu7onary(theories(
Hologenome(theory
Hologenome(theory(
• The(unit(of(natural(selec7on(is(the(holobiont:(the(organism(
together(with(its(associated(bacterial(communi7es,(that(
live(together(in(symbiosis.(
• The(holobiont(can(adapt(to(changing(environmental(
condi7ons(far(more(rapidly(than(by(gene7c(muta7on(and(
selec7on(alone.((
• Darwinism(emphasises(compe$$on((survival(of(the(fitest),(
hologenome(theory(also(includes(coopera$on((through(
symbiosis)

24. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 86
Evolu7onary(theories(
Hologenome(theory
Hologenome(theory(in(so#ware(evolu7on?(
!
Hologenome(theory(may(be(closer(to(what(one(observes(in(
open(source(projects(where(coopera$on(plays(a(more(
important(role.

25. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 87
Trophic(web((food(chain)
in(natural(ecosystems

26. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 88
Trophic(web(in
so#ware(ecosystems
Producer?consumer(rela7on
Users
Peripheral(
developers
Core(developers
Onion(model
TOP?DOWN(
change(requests(
&(bug(reports
BOTTOM?UP(
changes(in(core(
projects(and(
architecture(
Nakakoji(et(al.(Evolu$on/paQerns/of/openUsource/
soCware/systems/and/communi$es.(IWPSE(2002.(

27. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 89
Ecosystem(Dynamics
PredatorIprey6rela&onship
• An(instance(of(the(
consumer?resource(
rela7onship(
• Predators((hun7ng(animals)(
feed(upon(their(prey(
(atacked(animals)
Dynamic(model
• Two(mutually(dependent(
parametric(differen7al(
equa7ons
(Lotka?Volterra(1925/1926)

28. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 90
So#ware(Ecosystem
Dynamics
PredatorIprey6rela&onship6in6so9ware6ecosystems?
• Debuggers(are(predators,(so#ware(defects(are(prey(
Calzolari/et/al./Maintenance/and/tes$ng/effort/modeled/by/linear/and/
nonlinear/dynamic/systems,”/Informa$on/and/SoCware/Technology,/43(8):/
477/–/486,/2001

29. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering
• Stability/
• the(capacity(to(maintain(an(equilibrium(over(longer(periods(of(7me(
• Resistance/
• the(ability(to(withstand(environmental(changes(without(too(much(
disturbances(of(its(biological(communi7es(
• Resilience/
• the(ability(to(return(to(an(equilibrium(a#er(a(disturbance
Desirable(ecosystem(characteris7cs
91

30. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering
• Stability/
• the(capacity(to(maintain(an(equilibrium(over(longer(periods(of(7me(
• Resistance/
• the(ability(to(withstand(environmental(changes(without(too(much(
disturbances(of(its(biological(communi7es(
• Resilience/
• the(ability(to(return(to(an(equilibrium(a#er(a(disturbance(
!
Higher(biodiversity(favours(these(characteris7cs
Desirable(ecosystem(characteris7cs
92

31. July?August(2014(—(NATO(Marktoberdorf(Summer(School(—(Dependable(So#ware(Systems(Engineering 93
Desirable(ecosystem(characteris7cs(
Biodiversity
Biodiversity((of(species)(measures(
the(degree(of(varia7on(of(species(
within(a(given((natural)(ecosystem(
• Many(different(metrics:(
• species(richness(
• species(evenness(
• Shannon(diversity(index(
• Simpson(index(
• …
Goal:(Use(these(and(related(measures(to(study(maintainability(and(
survivability(of(so#ware(projects(within(their(ecosystem