Interactive Systems Engineering: A Pattern-Oriented and Model-Driven Architecture

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1 Iteractive Systems Egieerig: A Patter-Orieted ad Model-Drive Architecture M. Taleb Huma-Cetred Software Egieerig, Group Cocordia Uiversity, Motreal, Quebec, Caada Telephoe: ext 7166 mtaleb@ecs.cocordia.ca A. Seffah Huma-Cetred Software Egieerig Group Cocordia Uiversity Motreal, Quebec, Caada Telephoe: ext.3024 seffah@cse.cocordia.ca A. Abra Software Egieerig Departmet & Iformatio Techology, École de Techologie Supérieure (ÉTS), Motreal, Quebec, Caada Telephoe: ext alai.abra@etsmtl.ca Abstract Iteractive applicatios are desiged usig profoud kowledge about the busiess domai, domai objects, fudametal domai-related priciples, ad user tasks. Noetheless, the reuse of kowledge i the format of patter have ot impacted at the architectural level, they are still mostly used for techical problems. For example the followig desig cocers eed to be addressed at the architectural, such as: (1) decouplig the various aspects of iteractive systems (for example, busiess logic, the UI, avigatio, ad iformatio architecture) ad (2) isolatig platform specifics from the cocers commo to all iteractive systems. I this paper, we preset POMA architecture which illustrates how several idividual models ad patters ca be combied at differet levels of abstractio ito heterogeeous structures which ca the be used as buildig blocks i the developmet of iteractive systems to solve a pool of prove solutios to these problems ad how patters ca supplemet the model drive architecture. Keywords:, Models, Architecture, Iteractive Systems, POMA, MDA. 1 Itroductio Over the past two decades, research o iteractive systems ad user iterfaces (UI) egieerig has resulted i several architectural models which costitute a major cotributio ot oly to facilitate the developmet ad maiteace of iteractive systems, but also to promote the stadardizatio, portability ad ergoomic "usability (ease of use) of the iteractive systems beig developed. Several iteractive system architectural models have bee itroduced. Buschma et al. defie architectural models as [1]: the structure of the subsystems ad compoets of a system ad the relatioships betwee them typically represeted i differet views to show the relevat fuctioal ad o fuctioal properties. This defiitio itroduces the mai architectural compoets (for istace, subsystems, compoets, ad coectors) ad covers the ways i which to represet them, icludig both fuctioal ad o-fuctioal requiremets, by meas of a set of views. A umber of architectures specific to iteractive systems have bee proposed, e.g., Seeheim model [2] ad [3], Model-View-Cotroller (MVC) (Goldberg, 1984), Aget Multi-Faceted (AMF) [4] which is a extesio of MVC, Arch/Sliky [5], Presetatio Abstractio Cotrol (PAC) [6] ad [7], PAC-Amadeus ad Model-View- Preseter (MVP) [8]. Most of these architectures cosist of three mai elemets: (1) abstractio or model, (2) cotrol or dialog ad (3) presetatio. Their goal is to improve ad facilitate the desig of iteractive systems. However, eve though the priciple of separatig a iteractive system ito compoets has its desig merits, it ca also be a source of serious adaptability ad usability

2 problems i systems which provide fast, frequet, ad itesive sematic feedback: the commuicatio betwee the view ad the model makes the iteractive system highly coupled ad complex. have bee proposed to alleviate some of these weakesses, ad ideed were itroduced based o the observatio give by Alexader [9] i sectio 2. Such a patter provides, o a sigle level, a pool of prove solutios to may of the recurrig weakesses. have prove their utility i differet fields of applicatio. I 2001, the Object Maagemet Group itroduced the Model-Drive Architecture (MDA) iitiative as a architecture to iteractive system specificatio ad iteroperability based o the use of formal models (i.e. defied ad formalized models). The mai idea behid MDA is to specify busiess logic i the form of abstract models. These models are the mapped (partly automatically) to differet platforms accordig to a set of trasformatio. The models are usually described i UML i a formalized maer, which ca be used as iput for tools to perform the trasformatio process. I recet years, iteractive systems have matured from offerig simple iterface fuctioality to providig itricate processes such as ed-to-ed fiacial trasactios. Users have bee give more sophisticated techiques to iteract with available services ad iformatio usig differet types of computers. Differet kids of computers ad devices (icludig, but ot limited to, traditioal office desktops, laptops, palmtops, PDAs with ad without keyboards, mobile telephoes, ad iteractive televisios) are used for iteractig with such systems. Oe of the major characteristics of such crossplatform iteractive systems is that they allow a user to iteract with the server-side services ad cotets i various ways. Iteractive systems for small ad mobile devices are resource costraied ad caot support a full rage of iteractive system features ad iteractivity because of the lack of scree space or low badwidth. Oe importat questio is how to develop ad deploy the same system for differet platforms without architecturig ad specifically writig code for each platform, for learig differet laguages ad the may iteractive systems desig guidelies that are available for each platform. I our cotiued research project, the goal ca be stated as follows: Defie a ew architecture to facilitate the developmet ad migratio of iteractive systems while improvig their usability ad quality. To pursue this goal, the research objective is to develop a ew architecture which is called, Patter-Orieted ad Model- Drive Architecture (POMA) preseted i Figure 2. POMA will be based o the cocepts of N-tiers architectures (MVC, J2EE, Zachma), Patter-Orieted Desig (POD), Patter-Supported Approach (PSA), ad Model-Drive Architecture (MDA). The Figure 1 summarizes the architectural patters ad models that were combied to obtai the POMA architecture. Figure 1: Architectural ad Models 2 Backgroud work Itroduced by [10], desig patters ca be viewed as buildig blocks that may be composed of several compoets to create desigs. A sigle patter describes a problem that appears costatly i the eviromet with a correspodig solutio to this problem expressed i a way that allows desigers to reuse this solutio for differet platforms. For cross-platform iteractive systems, patters are iterestig for followig three reasos. Refer to [1] for a more geeral discussio o patters ad their beefits: They come from experimets o established experieces ad were ot created artificially; They are a meas of documetig architectures; I the case of cross-platform developmet, they provide for the possibility for a team to have a commo visio ad laguage. Patter-Orieted Desig (POD) itroduces a architecture for "composig" prove desig patters ito reliable, robust large-scale software systems. However, the developmet of web applicatios usig desig patters as desig compoets requires a careful look at compositio techiques. Several methods have bee proposed for compositio. For example, [11] proposed two compositio techiques: Behavioural compositio techiques that are based o object iteractio specificatios to show how istatiatios of patters ca be composed; Structural compositio techiques which are based o the static architectural specificatios of composed istatiated patters usig class diagrams. The patter-supported approach (PSA) to the user iterface desig process suggests a wider scope for the use of patters by lookig at the overall desig process. Based

3 o the fact that the usability of a system emerges as the product of the user, the task ad the cotext of use, PSA itegrates this kowledge i most of its patters, dividig the forces i the patter descriptio correspodigly (i.e., describig Task, User, ad Cotext forces). PSA provides a double-liked chai of patters (parts of a emergig patter laguage) that support each step of the desig process [12]. Buildig o PSA, the proposed approach highlighted aother importat aspect of patter-orieted desig: patter combiatio. By combiig differet patters, developers ca utilize patter relatioships ad combie them i order to produce a effective desig solutio. As a result, patters become a more effective vehicle that supports desig reuse. I 2001, the Object Maagemet Group itroduced Model-Drive Architecture (MDA) as a approach to system specificatio ad iteroperability based o the use of formal models (i.e., defiite ad formalized models) [13]. The mai idea of MDA is to specify busiess logic i the form of abstract models. These models are the mapped (partly automatically) accordig to a set of trasformatio to differet platforms. The models are usually described by UML i a formalized maer which ca be used as iputs for tools which perform the trasformatio process. The mai beefit of MDA is the clear separatio of the fudametal logic behid a specificatio from the specifics of the particular middleware that implemets it. The MDA approach distiguishes betwee the specificatios of the operatio of a system ad the details of the way that the system uses the capabilities of its platform. POMA is to be based o the specificatio of software architecture for iteractive systems, where software architecture meas: the descriptio of the subsystems ad compoets of a software system ad the relatioships betwee them, typically represeted i differet views to show the relevat fuctioal ad o fuctioal properties [1]. This defiitio itroduces both the mai architecture elemets (subsystems, compoets, coectors), how to represet them (by meas of a set of differet views) ad what they actually reflect (both fuctioal ad o fuctioal requiremets). The basic architecture that is cosidered as a startig poit is MVC [14] ad [15] patter implemetatio i Java laguage. Such a implemetatio exploits the Observer Iterface ad Observable classes. The MVC is a 3-tier architecture with a classic desig patter ofte used by a iteractive systems architecture that eeds the ability to maitai multiple views of the same data. The MVC patter depeds o a clea separatio of objects ito oe of three compoets or levels (Model, View, ad Cotroller). Buildig o the MVC patter, the Java Su team proposes a 5-tier architecture to model Core J2EE Architecture (Java Based Architecture). This architecture is divided ito five levels of patters (Browser, Presetatio, Busiess logic, Midleware, ad Persistece). Thus, the proposed architecture is desiged to be geeric ad comprised of six levels of patters. This is based o the Zackma framework [16], which also has six categories of patters. Zackma proposed a Multi-tiered architecture represeted i a Eterprise Architecture schema i which he depicted two distict dimesios i a matrix. The colum classifies aswers to the iterrogatives: What (Data), How (Fuctio), Where (Network), Who (People), Whe (Time) ad Why (Motivatio). The rows classify the audiece perspectives of the scope, ower, desigers, builder, trades ad fuctioig eterprise. This gives 36 cells which uiquely classify portios of the eterprise. Cosiderig this Zackma framework [16], a patterorieted iteractive system six-tier architecture is proposed for POMA. The matrix classificatio of Zachma is o the colums iterrogatives; ad the rows are the six architectural levels ad categories of patters defied i [17], [18] ad [20]. 3 The proposed POMA Architecture To tackle some of the weakesses idetified i related work, set of cocepts, proposes a 6-tier architecture of patter-orieted ad model-drive geeric classificatio schema for a iteractive systems. The proposed POMA architecture (Figure 2) for iteractive systems developmet is a architecture comprisig five architectural levels of models usig six categories of patters of software architecture. The POMA architecture (Figure 2) icludes: Six architectural levels ad categories of patters [17], [18] ad [20] Te models, five of which are ad five others [19]; Four types of relatios used i POMA architecture, which are: 1. Compositio: used to combie differet patters to produce a by applyig the compositio [17] ad [20]; 2. Mappig: used to build a which becomes a by applyig the mappig ( ) [17] ad [20]; 3. : used to establish the relatioship betwee two models ( ) ad / or ( ) by applyig the trasformatio ;

4 4. Geeratio: used to geerate the source code of the whole iteractive system by applyig the geeratio code. The directio i which to read the POMA architecture i Figure 2 is as follows: Vertically, cocers the compositio of the patters to produce te PIM ad PSM models; Horizotally, cocers the compositio ad mappig of the patters to produce five PIM ad five PSM models, ad the geeratio of the source code for the whole iteractive system. 1. Navigatio 2. Iteractio 3. Visualizatio 4. Presetatio 5. Iteroperability 6. Iformatio Architectural Level ad Categories of POMA : Patter-Orieted ad Model-drive Architecture PIM : Platform Idepedet Model PSM : Platform Specific Model The Symbol Laguage used Compositio Compositio Represets a iteractio PIM Domai Model T1 Task Model T2 Dialog Model T3 Presetario Model T4 Layout Model (PIM to PIM) ad/or (PSM to PSM) Mappig Mappig (PIM to PSM) (PSM to source code) Code Geeratio PSM Domai Model T 1 Task Model T 2 Dialog Model T 3 Presetatio Model T 4 Layout Model Laguage used Figure 2: POMA architecture for iteractive systems developmet Geeratio Iteractive Syatem Source Code The justificatios for POMA are as follows: 1. The N-tiers architectures such as MVC which is 3-tiers architecture, J2EE which is a 5-tier architecture, ad Zachma which is a multitiered architecture allow POMA architecture to iherit the cocept of architectural levels; 2. The POD architecture based o compositio techiques such as behavioral ad structural techiques of patters allows POMA architecture to iherit the cocept of these compositio techiques; 3. The PSA architecture based o the categories of patters allows POMA architecture to iherit the cocept of this categorizatio of patters; 4. The MDA architecture based o types of models such as PIM ad PSM, ad their trasformatio ad mappig, allows POMA architecture to iherit the cocept of models (PIM ad PSM) ad the cocepts of model trasformatio ad mappig. 4 Illustrative case study This sectio describes the desig illustratig ad clarifyig the core ideas of the POMA approach ad its practical relevace. The iteractive system ad correspodig models will ot be tailored to differet platforms. This case study illustrates how patters are used to establish the various models, as well as the trasformatio of oe model ito aother while respectig the patter compositio described i [17] ad [20] ad the patter mappig described [17] ad [20]. This example presets a geeral overview of the PIM ad PSM models iteractive system by applyig patter compositio ad mappig for the Task model of POMA architecture for a PDA platform. Table 1 lists the patters that will be used by the iteractive system. Patter Name Fid Summary) Path (Breadcrumb) Idex Browsig Model Type Task Task Task Problem The eed to fid idicators related to the task cocered, to fid evirometal patters related to the idicators, ad to fid a presetatio tool to display the results of the idicators ad the evirometal patters. The eed to costruct ad display the path that combies the data source, task, ad/or subtask. The eed to display all idicators listed as idex browsig to avigate ad select the desired oes. Adapter Task The eed to covert the iterface of a class ito aother iterface that cliets expect; a adapter lets classes work together which could ot otherwise do so because of iterface icompatibility. Builder Task The eed to separate the costructio of a complex object from its represetatio, so that the same costructio process ca create differet represetatios. List Task The eed to display the iformatio usig forms. Table Task The eed to display the iformatio i tables. Map Task The eed to display the iformatio i geographic maps.

5 Graph Task The eed to display the iformatio i graphs. Home Page Task The eed to defie the layout of a iteractive system home page, which is importat because the home page is the iteractive system iterface with the world ad the startig poit for most user visits. Table 1: Patter Summary for a PDA Task model The Figure 3 shows The -idepedet Task model which is obtaied by composig patters ad applyig the compositio [17] ad [20]. (PDA) P9. Adapter Idetical P9. Adapter P9. Adapter P10. Builder Idetical P10. Builder P10. Builder P11. List Idetical P11. List P11. List P12. Table Idetical P12. Table P12. Table P13. Map Idetical P13. Map P13. Map P14. Graph Idetical P14. Graph P14. Graph P15.Home Page Idetical P15.Home Page P15.Home Page Table 2: Example of patter mappig of the Task model for PDA platform After the mappig, the PSM Task model is obtaied for a PDA platform Figure 4. Navigatio 0 Iteractio 0 0 Path Patter IdexBrowsig Patter Fid Search Patter Browse Patter Summary Patter Shorter BreadCrumb Trial Patter Drop-Dow History Meu Patter Drop-Dow Meu Patter Iteroperability Adapter Patter Builder Patter Presetatio Figure 3: UML class diagram of a PIM Task model for a PDA platform Table 2 shows the mappig [17] ad [20] for the Task model patters for a laptop ad a PDA platforms. of Microsoft Platform P6.Fid Summary) P7.Path (Breadcrumb) P8.Idex Browsig Type of Mappig -Idetical, Scalable -Idetical, Scalable (Laptop) -Scalable Fudametal (PDA) or -Idetical (Laptop) -Fudametal Replacemet patters for Laptop platform P6.Fid Summary P7.Path (Breadcrumb) P8.Idex Browsig Replacemet patters for PDA platform P6.Fid Summary) - P7.1s Shorter Bread Crumb Trial -P7.2 Dropdow History meu P8.Drop-dow meu List Patter Table Patter Map Patter Graph Patter HomePage Patter Figure 4: UML class diagram of a PSM Task model for a PDA platform To use path (BreadCrumb) Patter o the PDA platform, we eed to isert Short BreadCrumb Trial ad Drop dow History Meu patters to obtai iformatio lik path i a umber smaller portal displays. The same desig that has doe for other PIM ad PSM models such as: Domai model, Dialog model, Presetatio model ad Layout model of POMA architecture. 5 Coclusio ad further work I this paper, a ovel practical multi-platform architecture is itroduced for iteractive systems egieerig. This architecture combies patter ad model to facilitate the egieerig of multi-platform applicatios icludig traditioal computer, PDA with ad without keyboards, mobile phoe, iteractive televisio, laptop ad palmtop. POMA proposed six architectural model combiig two key approaches: model-drive ad patter-orieted. POMA proposed a architectural level

6 ad categories of patters (Navigatio patters, Iteractio patters, Visualizatio patters, Presetatio patters, Iteroperability patters, ad Iformatio patters) i [17], [18] ad [20], as well as the various relatioships betwee patters [17] ad [20]. These relatioships are used to combie ad map several types of patters to create a patter-orieted desig for iteractive systems, as well as to show how to geerate specific implemetatios suitable for differet platforms from the same patter-orieted desig. The, POMA proposed five categories of models (Domai model, Task model, Dialog model, Presetatio model, ad Layout model) [19] to address some of the challegig problems, such as: (a) decouplig the various aspects of iteractive systems, such as busiess logic, UI, avigatio, ad iformatio architecture; ad (b) isolatig platformspecific problems from the cocers commo to all iteractive systems. Amog the ext steps required to develop POMA are: The creatio of differet model trasformatio to trasform oly the PIM ad PSM models betwee them such as: PIM to PIM, ad PSM to PSM Descriptio of a process for the geeratio of a source code from the five PSM models of POMA; Developmet of a tool that automates the POMA architecture-based egieerig process; Stadardizatio of POMA architecture to all types of systems, ot oly to multi-platform iteractive systems; Quality Assurace of the applicatios produced, sice a patter-orieted architecture will also have to permit the ecapsulatio of quality attributes ad to facilitate predictio; Validatio of the migratio, the usability ad overall quality of POMA architecture for iteractive systems usig differet existig methods; Evaluatio of the effectiveess ad learig time of POMA architecture for ovices ad experts users. 6 Refereces [1] F. Buschma, R. Meuier, Rohert H., P. Sommerlad ad M. Stal, Patter-Orieted Software Architecture: A System of, Joh Wiley & Sos Ltd, [2] G. Pfaff, User Iterface Maagemet System, Seeheim Workshop, 1985, Spriger-Verlag, Berli, Germay. [3] M. Gree, User Iterface Maagemet System, ACM, Volume 19, No.3, 1985, The Uiversity of Alberta, Alberta, Caada. [4] K. E. Ouadou, AMF : u modèle d architecture multi- Agets Multi-Facettes pour iterfaces homme-machie et les outils associés, Thèse de doctorat, 1994, École Cetrale de Lyo, Frace. [5] C. Gram ad G. Cockto (Eds), Desig Priciples for Iteractive Software, Chapma & Hall, [6] J. Coutaz, PAC, a implemetatio Model for dialog Desig, Iteract 87, pp , 1987, Stuttgart, Germay. [7] J. Coutaz, Architecture Models for iteractive software: Failures ad treds, I Egieerig for Huma- Computer Iteractio, G. Cockto Ed, Elsevier Sciece Publicatio, Pp , [8] L. Bass, P. Clemets ad R. Kazma, Software Architecture i Practice, Secod Editio, Addiso- Wesley, 2003, Bosto: (MA), USA. [9] C. Alexader, the Timeless Way of Buildig, Oxford Uiversity Press, 1979, New York: (NY), USA. [10] C. Alexader, S. Ishikawa, M. Silverstei, M. Jacobso, I. Fiskdahl-Kig ad S. Agel, A Patter Laguage, Oxford Uiversity Press, 1977, New York, USA. [11] S. Yacoub, H. Ammar, Compositio of Desig, Addiso Wesley Professioal, ISBN , 416 pages, 2003, Hardcover, Germay. [12] Å. Gralud, D. Lafreière, D. A. Carr, A Patter- Supported Approach to the User Iterface Desig Process, Proceedigs of HCII 2001, 9th Iteratioal Coferece o Huma-Computer Iteractio, August 5-10, 2001, New Orleas, US. [13] D. D Souza, Model-Drive Architecture ad Itegratio Opportuities ad Challeges, OMG Group, 2001, at ftp://ftp.omg.org/pub/docs/ab/ pdf. [14] E. Gamma, R. Helm, R. Johso ad J. Vlissides, Desig : Elemets of Reusable Object-Orieted Software, Addiso Wesley, [15] A. Goldberg, Smaltalk-80: The Iteractive Programmig Eviromet, 1984, Addiso-Wesley Publicatio. [16] J. A. Zachma, A Framework for Iformatio Systems Architecture, IBM Systems Joural, Vol. 26, No. 3, 1987, IBM Publicatio, G

7 [17] M. Taleb, H. Javahery ad A. Seffah, Patter- Orieted Desig Compositio ad Mappig for Cross- Platform Web Applicatios, the XIII Iteratioal Workshop. DSVIS 2006, Triity College Dubli Irelad, DOI / , ISBN , Vol. 4323/2007, Publisher Spriger-Verlag, Berli Heidelberg, Germay. [18] M. Taleb, A. Seffah ad A. Abra, Patter-Orieted Architecture for Web Applicatios, 3rd Iteratioal Coferece o Web Iformatio Systems ad Techologies (WEBIST 2007), 2007, ISBN , pp , Barceloa, Spai. [19] M. Taleb, A. Seffah ad A. Abra, Model-Drive Desig Architecture for Web Applicatios, the 12th Iteratioal Coferece o Huma Cetered Iteractio Iteratioal (FIC-HCII 2007), 2007, Beijig Iteratioal Covetio Ceter, Beijig, P.R. Chia, Vol. 4550/2007, pages , Publisher Spriger- Verlag, Berli Heidelberg, Germay. [20] M. Taleb, A. Seffah ad A. Abra, -Orieted Desig for Cross-Platform Web-based Iformatio Systems, The 2007 IEEE Iteratioal Coferece o Iformatio Reuse ad Itegratio (IEEE IRI-07), 2007, pages , Las Vegas, USA.