Improving the adaptation of web applications to different versions of software with MDA

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. Re e ences 1. K. Czane cki and U.W. Eisenecke . Gene a i e P og amming. Me hods, Tools and 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. 7. A. an Deu sen, E. Visse , and J. Wa me . Model-d i en so wa e e olu ion: A esea ch agenda. In P oc. In . Ws on Model-D i en So wa e E olu ion held wi h he ECSMR’07, 2007. 8. J. P. Wadsack and J. H. Jahnke. Towa ds model-d i en middlewa e main enance. In P oc. In . Wo kshop on Gene a i e Techniques in he con ex o Model-D i en A chi ec u e, 2002.