Imp o ing he adap a ion o web applica ions o
di e en e sions o so wa e wi h MDA
A. M. Reina Quin e o1, J. To es Valde ama1, and M. To o Bonilla1
Depa men o Languages and Compu e Sys ems
E.T.S. Ingenie ´ıa In o m´a ica.
A da. Reina Me cedes, s/n.
41007 Se ille, Spain
{ einaqu, j o es, m o o}@lsi.us.es
h p://www.lsi.us.es/~ einaqu
Abs ac . The Model-D i en A chi ec u e (MDA) has been p oposed
as a way o sepa a ing he de ails o an implemen a ion pla o m om he
p oblem domain. This pape shows ha his app oach is also good o
he adap a ion o so wa e o he di e en e sions o he same pla o m.
As an example, Sp ing Web Flow (SWF), a amewo k ha allows he
de ini ion and ep esen a ion o use in e ace lows in web applica ions,
has been chosen. A e six mon hs o e olu ion, he web lows de ined wi h
SWF 1.0 RC1 we e no compa ible wi h SWF 1.0. The pape analyzes he
changes in oduced by he new elease, and i p oposes an MDA-based
app oach o so en he impac o hese changes.
1 In oduc ion
The as e olu ion o echnology has caused he pe iod o ime ha companies
ake o p o iding new e sions o hei p oduc s be sho ened, i hey wan o
be up- o-da e. Many imes, new eleases o e new and imp o ed ea u es, bu
also cause backwa d incompa ibili y. This p oblem is s essed in open sou ce
p ojec s, because new e sions a e o en eleased ou due o hei con inuous
in e ac ion wi h end use s. The e o e, i is c ucial o adap so wa e p oduc s
ha a e being de eloped wi h hese amewo ks a a minimum cos .
On he o he hand, web applica ions a e becoming mo e and mo e complex,
and nowadays, hey a e mo e han jus simple in e connec ed web pages. Thus,
an impo an piece in i s de elopmen a e Web Objec s [4], ha is, pieces o com-
piled code, ha p o ide a se ice o he es o he so wa e sys em. These pieces
o code a e o en suppo ed by open sou ce amewo ks, and as a consequence,
he e olu ion o hese amewo ks has also become an impo an challenge in
web applica ion e olu ion.
The p ocess o eleasing ou new e sions o a amewo k o a so wa e
p oduc can be conside ed as a so wa e e olu ion p ocess. The e a e se e al
echniques o so wa e e olu ion ha ange om o mal me hods o ad-hoc
solu ions. Bu he mos p omising ones a e: eenginee ing, impac analysis ech-
niques, ca ego y- heo e ic echniques and au oma ed e olu ion suppo . MDA
also seems o be a p omising philosophy o dealing wi h so wa e e olu ion, no
only because i allows he sepa a ion o he domain conce ns om he echnolo-
gical conce ns, bu also because design in o ma ion and dependencies a e explici
in models and ans o ma ions, espec i ely.
This pape shows how he MDA philosophy can help us o adap easily o
a new elease o a amewo k he so wa e a i ac s p oduced wi h an ea lie
e sion. Fu he mo e, i analyzes he e olu ion p ocess in he MDA. To demon-
s a e he bene i s o his philosophy, he pape will be based on a case s udy.
The case s udy desc ibes how a web low de ined wi h Sp ing Web Flow 1.0-RC1
can be adap ed o Sp ing Web Flow 1.0, a mo e s able elease. Sp ing Web Flow
(SWF)1is a componen o he Sp ing F amewo k’s web s ack ocused on he
de ini ion and execu ion o use in e ace (UI) lows wi hin a web applica ion.
A use in e ace low can be conside ed as pa o he na iga ion p ocess ha a
use has o deal wi h while in e ac ing wi h a web applica ion. Fo he sake o
ha ing a clea idea o he pe iod o ime be ween he wo s eleases, i should be
highligh ed ha SWF 1.0 RC1 was ou in May 2006, while SWF 1.0 was pub-
licly accessible in Oc obe 2006. And, al hough bo h e sions sha e mos o he
concep s, he e a e some echnical de ails ha di e and ha cause backwa d
incompa ibili y.
The es o he pape is s uc u ed as ollows: In sec ion 2, he p oblem is
in oduced by example, ha is, he wo king example is explained and p ob-
lems a e b ie ly highligh ed. Secondly, he app oach is explained ollowing h ee
s ages: me amodel and an o ma ion de ini ions, e olu ion analysis and change
p opaga ion. A e ha , some ela ed wo ks a e enume a ed and, a las , he
pape is concluded and some u u e lines o wo k a e poin ed ou .
2 P oblem S a emen
Due o he cons an e olu ion o echnology, new e sions o so wa e p oduc s
a e eleased ou mo e and mo e equen ly. This cycle o new e sions is spe-
cially speeded up when dealing wi h open sou ce p oduc s. This is due o use
pa icipa ion: use s a e cons an ly sending epo s abou mis akes. In his con-
ex , a equen ope a ion is so wa e mig a ion, hus he s udy case is going
o be ocused on a mig a ion om Sp ing Web low 1.0 RC1 o Sp ing Web low
1.0, a new, mo e s able elease, which appea ed jus 6 mon hs a e he public
appea ance o he 1.0 RC1 elease.
A low de ines a use dialog ha esponds o use e en s o d i e he execu ion
o applica ion code o comple e a business goal. And, al hough he elemen s
o cons uc s needed o de ine a web low a e he same in bo h e sions, he
echnical de ails di e om one elease o he o he . As a consequence, he e is
no backwa d compa ibili y.
In o de o be clea enough, he low used as s udy case is simple, bu i
co e s he main issues needed. The ini ial example has been ob ain om [2],
1The Sp ing Web Flow Home Page: h p://opensou ce.a lassian.com/
con luence/sp ing/display/WEBFLOW/Home
and can be seen as pa o he na iga ion pa h om a simple e-shop web si e.
The low simula es pa o he dialog ha akes place when a use wan s o buy
ce ain p oduc . The na iga ion s eps ha a use has o pass h ough o buy
some hing a e: Fi s ly, selec he S a link. Secondly, en e his pe sonal da a.
Thi dly, selec he p ope ies o he p oduc . And, inally, a e pushing he Buy
bu on, he will ob ain a message epo ing abou he shopping.
<<Ac ionS a e>>
se upFo m
<<Ac ionS a e>>
bindAndValida ePe sonalDe ails
<<ViewS a e>>
pe sonalDe ailsView
success submi
<<DecisionS a e>>
es Quan i y
ue
<<ViewS a e>>
o de De ailsView
<<Ac ionS a e>>
bindAndValida eO de De ails
<<EndS a e>>
submissionSuccess
[${ lowScope.o de .cancelled}]
success
e o
alse
buy
oPe sonalDe ails
e o
success
<<ViewS a e>>
pe sonalDe ailsView
<<ViewS a e>>
o de De ailsView
success
<<DecisionS a e>>
es Quan i y
ue
<<EndS a e>>
submissionSuccess
[${ lowScope.o de .cancelled}]
alse
oPe sonalDe ails
success buy
<<ViewS a e>>
pe sonalDe ailsView
<<ViewS a e>>
o de De ailsView
success
<<DecisionS a e>>
es Quan i y
ue
<<EndS a e>>
submissionSuccess
[${ lowScope.o de .cancelled}]
alse
oPe sonalDe ails
success buy
(a) SWF 1.0 RC1 low
(b) SWF 1.0 low
Fig. 1. S a e cha co esponding o he web low speci ied in SWF 1.0 RC1
The implemen a ion o his dialog using SWF equi es he de ini ion o a web
low. This web low can be speci ied in wo di e en ways, by means o an XML-
ile o using a Ja a-code. I is a good echnique o d aw a s a e cha in o de
o unde s and he web low be e . The low consis s o six s a es (Fig. 1(a)):
h ee Ac ionS a e’s, wo ViewS a e’s and one DecisionS a e. Ini ially, he
low s a s i s execu ion by an Ac ionS a e which is in cha ge o se ing up he
o m. Then, he o m is displayed h ough he pe sonalDe ailsView s a e. A e
ha , he low en e s in o ano he Ac ionS a e, which will bind and alida e he
da a in oduced by he use . I he e a e any p oblems wi h da a, he low will go
back again o he pe sonalDe ailsView s a e; o he wise, i will en e in o he
o de De ailsView s a e, and he p ocess will be epea ed. Finally, i all da a a e
igh , he low will en e in o he es Quan i y s a e, a DecisionS a e, ha
can ou e he low depending on he alue o he a ibu e cancelled. Howe e ,
i he low e ol es in o de o be SWF 1.0 complian , we ha e he s a e cha
shown in Figu e 1(b). The numbe o s a es has been educed om six o h ee.
Tha is, all he Ac ionS a e’s ha e disappea ed.
3 The app oach
3.1 Me amodel and ans o ma ion de ini ion
The i s s ep in he app oach is o ob ain a me amodel which exp esses he
conce ns ha a e implici in he amewo k and hei ela ionships. In ou case
s udy, a me amodel o Sp ing Web Flow is needed. In his case, wo di e en
me amodels should be de ined, one o he SWF 1.0 RC1, and he o he one
o SWF 1.0. The g ea ad an age he e is ha , a his poin , bo h me amodels
should no di e oo much. The models con o ming o hese me amodels a e also
needed. I is likely ha we ha e models con o ming o SWF 1.0 RC1, bu i he
model-d i en p ocess has been no ollowed, some eenginee ing echniques could
be applied o ob ain hem. Finally, a se o ans o ma ions o ob aining he
code should be gi en, whe he model- o- ex o model- o-model ans o ma ions.
Fu he mo e, wi h all hese a i ac s, an analysis should be done in o de o
de e mine he kind o e olu ion ha has been en e ed in o he new elease o
he amewo k.
3.2 Analysing he e olu ion
In o de o ace up o he adap a ion p ocess, he a i ac s ha a e subjec o
change should be iden i ied, and also, which o hese changes should be classi-
ied as e olu ion. In MDA he e a e h ee ways o e olu ion: model e olu ion,
ans o ma ion e olu ion and me amodel e olu ion. In model e olu ion, changes
o sou ce models mus be mapped in o changes o a ge models h ough he
ans o ma ion ules. In ans o ma ion e olu ion, changes o he ans o ma ion
de ini ion mus be mapped in o changes o a ge models. Finally, in me amodel
e olu ion, changes o a me amodel mus be mapped o changes o desc ibed
models, plus o ans o ma ion de ini ions.
This sec ion will analyze he di e en changes in oduced in he Sp ing Web
Flow amewo k, and i will classi y hem acco ding o he ways o e olu ion in
MDA. In ou s udy case, he main changes in oduced o Sp ing Web Flow a e:
1. F om DTD’s o XMLSchemas. Al hough s uc u ally, his change is im-
po an , concep ually is e y simple. The only hing o do is o de ine a new
se o model- o- ex ans o ma ions. And, i he model- o- ex ans o me
is based on empla es, we only ha e o modi y he empla e. This is a kind
o model e olu ion.
2. Changing he oo and he ini ial s a e. This change is also simple.
While in SWF 1.0 RC 1, he oo o he XML web low was <web low> in
SWF 1.0, he oo is < low>. Mo eo e , he way o speci ying he s a s a e
has also been modi ied: in SWF 1.0 RC, he ini ial s a e was speci ied as an
a ibu e o he oo elemen <web low id="o de Flow" s a -s a e="¬
se upFo m">; howe e , in SWF 1.0, i is de ined as an XML elemen <s a -
s a e id e ="pe sonalDe ailsView"/>. These modi ica ions only imply
he empla e ede ini ion. This is a kind o model e olu ion.
3. New ende Ac ion p ope y in he ViewS a e This change is due o
he in oduc ion o a new p ope y ende Ac ion belonging o ViewS a e.
Bu his new p ope y implies a bi o concep ual change, because we should
change he design o he low in o de o ake ad an age o he ad anced
ea u es o he amewo k. Thus in SWF 1.0 RC1 an ini ial Ac ionS a e
was needed in o de o se up ini ially a o m. I we look a he Figu e 1, we
will see ha he s a s a e is an Ac ionS a e named se upFo m. Howe e ,
in SWF 1.0 his can be ep esen ed by a p ope y < ende -ac ions> linked
o he ViewS a e ha is in cha ge o ende ing he o m. As a esul o he
new design, in he Figu e 1(b), he Ac ionS a e has comple ely disappea ed.
This is a kind o me amodel e olu ion.
4. Ac ions in ansi ions This change is no eally due o he new e sion o
SWF, bu due o he inexpe ience o he au ho s wi h SWF when wo king
wi h SWF RC1. Thus, wo s a es (one ViewS a e and one Ac ionS a e)
we e de ined in o de o speci y, on he one hand, a web o m, and on he
o he hand, he binding and alida ion o da a in oduced by he use in
ha o m. The e, he ViewS a e named pe sonalDe ailsView is ollowed
by he Ac ionS a e named bindAndValida ePe sonalDe ails, which is
in cha ge o he binding and alida ion o use da a. In ha low he e is
also ano he pai o s a es ha ollow he same pa e n o de De ailsView
and bindAndValida eO de De ailsView. Howe e , hese wo s a es can be
eplaced o jus one ViewS a e, and he alida ion and biding can be ig-
ge ed by he ansi ion, which implies he disappea ance o he Ac ionS a e.
Thus, i we compa e he Figu es 1(a) and 1(a), we will see ha he numbe o
s a es has been educed, and now, he bindAndValida ePe sonalDe ails
and bindAndValida eO de De ails ha e been missed. This is a kind o
ans o ma ion e olu ion.
3.3 Change p opaga ion
In o de o mig a e ou applica ion o be complian o he new e sion o he
amewo k, di e en ac ions should be unde aken. And he conc e e ac ion will
depend on he kind o e olu ion. The easies e olu ion o ace up o is he model
e olu ion. In his case, he only hing o do is e o mula e he se o model o
ex ans o ma ions de ined o gene a ing he XML-Web low iles.
The me amodel e olu ion implies no only he modi ica ion o he Sp ing
Web low me amodel, bu also he de ini ion o new model o ex ans o ma-
ions. In o de o mig a e he old Sp ing Web low models in o he new ones, wo
di e en s a egies can be ollowed: one based on ho izon al ans o ma ions, and
he o he one based on e ical ans o ma ions. Ho izon al ans o ma ions [1]
change he modula s uc u e o an applica ion a he same le el o abs ac ion.
I we hink in model ans o ma ions, sou ce models and a ge models should

be exp essed a he same abs ac ion le el. On he o he hand, e ical ans o -
ma ions [1] in ol e he ans o ma ion o a high abs ac ion le el model in o a
lowe le el one.
In he s a egy based on ho izon al ans o ma ions, besides he o iginal
model- o- ex ans o ma ions, a se o ho izon al model- o-model ans o ma-
ions has o be de ined. These ans o ma ions along wi h he o iginal and
e ol ed me amodels, and he o iginal model will be he inpu o a model ans-
o ma ion engine, which will p oduced he e ol ed model as ou pu . Applying
he model o ex ans o ma ions, he e ol ed Sp ing Web low will be ob ained.
The second s a egy is mo e aligned o MDA and i consis s on he de ini ion
o a new me amodel which cap u es only he ele an conce ns, ha is, i should
igno e hose elemen s ha a e pla o m dependen . This second app oach is a bi
mo e expensi e han he i s one, in he sense ha new a i ac s a e needed, and
hey a e concep ually mo e complex. Bu i also has some ad an ages. Fi s ly,
as he di e en e sions deal wi h he same concep s, i is likely ha he PIM
me amodel will no change e y o en, and he impo an modi ica ions should
be a he PSM and ans o ma ion le els. Secondly, wi h he second app oach
we ha e o de ine a new me amodel o he new e sion o he p oduc , bu many
imes, his new me amodel is e y simila o he one de ined o he p e ious
e sion, so his ask does no suppose oo much wo k. And, inally, i we de ine
a PIM me amodel, we can deal wi h he same concep s bu in o he pla o ms.
Finally he model e olu ion can be sol ed de ining a se o ho izon al ans o -
ma ions o e o mula e he old models. In his case, he me amodel emains he
same, and also he model o ex ans o ma ions.
4 Rela ed Wo k
The model-d i en so wa e e olu ion is a new a ea o in e es , hus in he 11 h
Eu opean Con e ence on So wa e Main enance and Reenginee ing a wo kshop
on model-d i en so wa e e olu ion has been held. In [7] a su ey o he p oblems
aised by he e olu ion o model-based so wa e sys ems is made and i is s a ed
ha Model-D i en Enginee ing equi es mul iple dimensions o e olu ion. Ou
app oach deals wi h h ee o hese dimensions. On he o he hand, in [6] he
d awbacks o model d i en so wa e e olu ion a e analyzed, and as a conclusion
he au ho s s a e ha a dual app oach is needed, ha is, o use equi emen s
e olu ion o gene a e he model speci ica ion and he es speci ica ion o alida e
he sys em. Ou app oach ollows a op-down app oach, bu , a his poin we
a e no in e es ed in alida ion o e i ica ion.
In [3] incompa ibili ies be ween models and me amodels caused by me a-
model e isions a e aced up. The p oposed app oach is based on he sync oniza-
ion o models wi h e ol ing me amodels, bu his app oach only deals wi h one
dimension o e oulu ion, he me amodel e olu ion. [5] p oposes a amewo k
whe e so wa e a i ac s ha can be ep esen ed as MOF-complian models can
be synch onized using model ans o ma ions, bu hey a e ocused on acea-
bili y o changes o so wa e models . Finally, in [8], a sys ema ic, MDA-based
p ocess o enginee ing and main aining middlewa e solu ions is ou line. In ou
app oach, SWF can be conside ed as pa o a co po a e middlewa e.
5 Conclusions and Fu he Wo k
This pape has poin ed ou how we can ake bene i o he MDA philosophy in
o de o ha e a be e adap a ion o he di e en e sions o he same so wa e
p oduc . To do so, a case s udy based on he Sp ing Web Flow amewo k has
been in oduced. An analysis o he changes in oduced in he new e sion o
he amewo k has been made. Fu he mo e, wo di e en app oaches based on
model ans o ma ions ha e been conside ed o ace o me amodel e olu ion. In
his case, he ollowing a i ac s a e needed: one SWF 1.0 RC1 me amodel, one
SWF 1.0 me amodel, one web low me amodel ( his one, a he PIM le el), wo
se s o model o ex ans o ma ions (one o ob aining he XML ile con o ming
o SWF 1.0 RC1, and ano he one o ob aining he XML con o ming o SWF
1.0); and, inally, a se o model o model ans o ma ions, which will ans o m
he web low model (a he PIM le el) in o a model o SWF 1.0 RC1 and SWF
1.0, espec i ely.
One o he u u e wo ks is he implemen a ion, ia web, o a me amodel
eposi o y, in such a way ha we can coun wi h he me amodels o he di e en
e sions o he amewo ks. Thus, a se o me amodels will be publicly a ailable
in o de o imp o e he adap a ion o di e en eleases o a amewo k.
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Applica ions. Addison Wesley, 2000.
2. S e en De ij e . Sp ing web low examined. Ja aLobby.
3. B. G uschko and D. S. Kolo os. Towa ds synch onizing models wi h e ol ing me a-
models. In P oc. In . Wo kshop on Model-D i en So wa e E olu ion held wi h he
ECSMR, 2007.
4. A. E. Hassan and R. C. Hol . A chi ec u e eco e y o web applica ions. In P o-
ceedings o he 24 d In . Con . on So wa e Enginee ing, 2002, pages 349–359, 2002.
5. I. I ko ic and K. Kon ogiannis. T acing e olu ion changes o so wa e a i ac s
h ough model synch oniza ion. In P oc. o he 20 h IEEE In e na ional Con e ence
on So wa e Main enance (ICSM’04), 2004.
6. H. M. Sneed. The d awbacks o model-d i en so wa e e olu ion. In P oc. In . Wo k-
shop on Model-D i en So wa e E olu ion held wi h he 11 h Eu opean Con e ence
on So wa e Main enance and Reenginee ing, 2007.
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he ECSMR’07, 2007.
8. J. P. Wadsack and J. H. Jahnke. Towa ds model-d i en middlewa e main enance.
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A chi ec u e, 2002.