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An MDA Approach for Goal-oriented Requirement Analysis in Web Engineering

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Web designers usually ignore how to model real user expectations and goals, mainly due to the large and heterogeneous audience of the Web. This fact leads to websites which are difficult to comprehend by visitors and complex to maintain by designers.
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  An MDA Approach for Goal-oriented RequirementAnalysis in Web Engineering Jos´e Alfonso Aguilar, Irene Garrig´os, Jose-Norberto Maz´on, JuanTrujillo (Lucentia Research Group, Department of Software and Computing Systems -DLSI, University of Alicante, Alicante, Spain {  ja.aguilar,igarrigos,jnmazon,jtrujillo } @dlsi.ua.es) Abstract: Web designers usually ignore how to model real user expectations andgoals, mainly due to the large and heterogeneous audience of the Web. This fact leadsto websites which are difficult to comprehend by visitors and complex to maintain bydesigners. In order to ameliorate this scenario, an approach for using the i*  modelingframework in Web engineering has been developed in this paper. Furthermore, due tothe fact that most of the existing Web engineering approaches do not consider how toderive conceptual models of the Web application from requirements analysis we alsopropose the use of MDA ( Model Driven Architecture ) in Web engineering for: (i) thedefinition of the requirements of a Web application in a Computational IndependentModel (CIM), (ii) the description of Platform Independent Models (PIMs), and (iii)the definition of a set of QVT ( Query/View/Transformation  ) transformations for thederivation of PIMs from requirements specification (CIM), thus to enable the automaticgeneration of Web applications. Finally, we include a sample of our approach in orderto show its applicability and we describe a prototype tool as a proof of concept of ourresearch. Key Words: MDA, Web engineering, goal-oriented requirements, requirements anal-ysis, model transformations Category: D.2.1, D.2.2 1 Introduction Web applications have certain characteristics that make them different from tra-ditional software or information systems such as the amount of information theyoffer ( content  ), the access to the different scenarios where they offer informa-tion ( navigation  ) and how providing information to the users (  functionality  ) of the website. These unique characteristics of Web applications have enforced newWeb engineering methodologies to cope with those new requirements and Webdevelopers need to adopt it [Casteleyn et al. 2007, Cachero and G´omez 2002,Casteleyn et al. 2005, Koch 2000, Ceri and Manolescu 2003].In this context, Web engineering approaches should consider how to gatherand process requirements of different stakeholders, resulting in a requirementsspecification. The term Requirements Engineering (RE) is widely used toindicate that only requirements elicitation is not enough, since requirementshave to be processed to resolve conflicts, prioritized, and captured in a consistentrequirements specification [Almeida et al. 2006].  Journal of Universal Computer Science, vol. 16, no. 17 (2010), 2475-2494submitted: 15/2/10, accepted: 30/8/10, appeared: 1/9/10 ©  J.UCS  However, due to the idiosyncrasy of the audience, traditionally methodologiesfor Web engineering have not taken into serious consideration the requirementanalysis phase. As mentioned above, Web applications have certain characteris-tics that make them different from traditional software or information systems.Currently, one of the main characteristics of Web applications is that they typ-ically serve large and heterogeneous audience, since respectively (i) everybodycan access to the website and (ii) each user has different needs, goals and prefer-ences. Interestingly, this is the opposite situation from the traditional softwaredevelopment where the users are well known. Due to the heterogeneity of theusers of a Web application any Web engineering method should consider a re-quirements analysis phase indicating the users needs and every feature that theWeb application must satisfy [Escalona and Koch 2004].Nevertheless, current effort for requirement analysis in Web engineering israther focused on the system and the needs of the users are figured out by thedesigner. This scenario leads us to websites that do not assure the achievementof  real  user requirements and goals, thus producing user disorientationand comprehension problems. Hence, there may appear development andmaintenance problems for designers, since costly, time-consuming and rathernon-realistic mechanisms (e.g. surveys among visitors) should be developed toimprove the already implemented website, thus increasing the initial projectbudget.Lately, MDA was established by the OMG (Object Management Group)as architecture for application development. MDA identifies three types of models: the Computational Independent Model (CIM), describes the businesslogic (requirements), the Platform Independent Model (PIM), which specifiesthe CIM logic independent of software technology platforms and, finally, thePlatform Specific Model (PSM) specifies the model in a specific technologyplatform. The key idea of this architecture is that if the software development isguided by models that represent the final developed software, some benefitswill be obtained in some aspects like functionality, interoperability andmaintenance [Brown 2004].As an alternative to solve the problems associated with RE, specifically inthe Web engineering field, in this paper, a complementary viewpoint shouldbe adopted: modeling which are the expectations, intentions and goals of theusers when they are browsing the site and determining how they can affect thedefinition of a suitable Web design.MDA-based proposals [Meli´a and G´omez 2006] have traditionally focused onthe definition of transformations from the PIM level to the code, optionallypassing through a PSM level. Unfortunately, these proposals usually ignore theCIM level where user requirements can be defined. Bearing these considerationsin mind, in this paper we introduce an MDA alignment with the proposal 2476  Aguilar J.A., Garrigos I., Mazon J.-N., Trujillo J.: An MDA Approach ...  DOMAIN  MODEL NAVEGATIONAL MODEL       C       I      M REQUIREMENTMODEL CODE       P      I      M PSM QVT Figure 1: Our MDA approach for goal-oriented requirement analysis in Webengineering.presented in [Garrig´os et al. 2009] to specify requirements in a model thatrepresents a CIM level in MDA. To this aim, we propose to use the i*  modeling framework [Yu 1995, Yu 1997], one of the most valuable approachesfor analyzing stakeholders’ goals and how the intended system would meetthem. For representing the PIM level in our approach we considered twoof the models (Domain and Navigational models) proposed by the A-OOHmethod [Garrig´os 2008] as a PIM.This approach is intended to support an automatic derivation of the Domainand Navigational models (PIMs) from the requirements model (CIM). In orderto achieve this, we have defined a set of QVT rules [QVT Specification]. Anoverview of our proposal can be seen in Figure 1.The remainder of this paper is structured as follows: Section 2 presentscurrent requirements analysis approaches for Web engineering. Our approachfor goal-oriented Web requirement analysis in an MDA context is presented inSect. 3. Section 4 describes an example based on an Online Bookstore to show theapplicability of our proposal. Section 5, describes the implementation framework  of our approach. Finally, in Sect. 6, we present our conclusions and sketch somefuture work. 2 Related Work Nowadays few approaches have focused on defining an explicit requirementanalysis (RA) phase to model the real user goals and needs in an MDA context.Some of them consider a requirements phase using techniques such as use casesand text templates among others [Aguilar et al. 2010], but as mentioned before,leaving aside the requirements specification from a CIM. Among the approaches,including RA in Web Engineering, we can stress the following:UWE ( UML-based Web Engineering  ) [Koch et al. 2006]. Regarding to therequirements specification, UWE initially used use case diagrams with tex-tual descriptions, currently this phase is carried out by means of UMLprofiles in combination with a metamodel called WebRE (developed by 2477  Aguilar J.A., Garrigos I., Mazon J.-N., Trujillo J.: An MDA Approach ...  the authors of NDT and UWE), more information can be consultedin [Escalona and Koch 2006]. Through the requirements model, UWE can gen-erate content, navigation, presentation and process models through a se-ries of QVT transformations. With regard to the implementation, a plugincalled MagicUWE was developed to be used within the CASE tool Magic-Draw (http://www.magicdraw.com) [Bush and Koch 2009], which allows UWEto provide a professional CASE tool, although it does not take into account theanalysis of requirements.NDT ( Navigational Development Techniques ) [Escalona and Arag´on 2008].Requirements are specified in NDT by using use case diagrams and textual tem-plates. When a complex application is developed with this approach, it is difficultto maintain due to the use of textual templates for requirements specification;in the words of the authors of the methodology: the templates are not easy to complete as they require intensive interviews [Escalona and Koch 2006]. TheRA phase and traceability is supported by the NDT-Suite tool (NDT-Profile,NDT-Driver-Quality NDT) by using profiles to work with Enterprise Architect(http://www.sparxsystems.com). By combining NDT, UWE and WebRE, theconceptual models (content, navigational and abstract interface) can be derivedfrom requirements specification [Escalona and Koch 2006]; the main drawbackof this approach is the lack of tool support for model-to-model transformations.WebML ( Web Modeling Language ) [Ceri et al. 2000]. In this method, adistinctive feature is the use of XML (eXtensible Markup Language) to representthe models (data, hypertext, presentation and customization) generated in eachstage of development. The RA phase is not described in detail, in [WebML], butauthors propose the use of UML use case and activity diagrams for requirementsspecification.WSDM ( Web Site Design Method  ) [De Troyer and Leune 1998]. Require-ments management is carried out through techniques such as concept maps (of roles and activities) and the data dictionary for the definition of functional andsecurity requirements. The form in which this approach considers the require-ments can cause precision errors when they are specified, because this is done ina textual form. The lack of transformations between models as well as the lackof a prototype tool which supports the requirements specification demonstratesthe limitations of this approach.OOHDM ( Object Oriented Hypermedia Design Model  ) [Schwabe 1998]. Thisapproach is based on the Object Oriented paradigm. The requirementsspecification is divided in (i) identification of roles, (ii) specification of scenarios,(iii) specification of Use Cases, (iv) specification of User Interaction Diagramsand (v) validation of User Interaction Diagrams and Use Cases. This approachdefines guidelines to define conceptual and navigational schemas by means of rules described in natural language, this rules indicate how the conceptual and 2478  Aguilar J.A., Garrigos I., Mazon J.-N., Trujillo J.: An MDA Approach ...  navigational schema can be defined from User Interaction Diagrams. OOHDMdoes not have a tool support for the RA phase. Furthermore, this approach doesnot support the definition of conceptual models from requirements specification.OOWS ( Object-Oriented Approach for Web Solutions ) [Fons et al. 2003].The RA phase is carried out through a set of strategies (i) FRT (FunctionRefinement Tree), (ii) Use Cases and (iii) Tasks, Task Specification andData Description Diagrams for navigation requirements. The authors arecurrently working on a technique for the specification of requirements throughontologies. The task analysis is a technique that in most cases where itis implemented is time-consuming, complex and depends largely on theexperience of the analyst for its correct implementation. Moreover, accordingto [Bolchini and Mylopoulos 2003], the user needs are not necessarily welldefined within his own mind as to be defined as tasks. In regard to tool support,this approach has an environment called OOWS-Suite [Valverde et al. 2007],which is integrated with the OlivaNova tool (http://www.integranova.com) toprovide support for requirements gathering phase. Table 1: Summary of methodological approaches. Approach Techniques Tool support Tool support for RA NDT Use cases, textual templates NDT-Tool NDT-ToolWebML Use cases, activity diagrams WebRatio NoWSDM Concept maps, data dictionary No NoUWE Use cases, UML profiles ArgoUWE MagicUWE, ArgoUWEOOWS Use cases, task diagrams, FRT OlivaNova OlivaNova, OOWS-SuiteOOHDM Use cases, User Interaction Diagrams, Conceptual maps OOHDM-WEB NoA-OOH Use cases, i*, UML profiles VisualWade Eclipse plugin Table 1 shows a summary of the reviewed approaches. It is shown a tendencytowards the application of UML profiles as a technique for requirementsspecification, and the persistence of other one, the use cases. Except WSDM,each approach has a tool to support it. In the requirements phase, only NDT,UWE, OOWS and A-OOH have a tool support.Is worth mentioning the support offered by the approaches WSDM, NDT,UWE and WebML through its website, they offer examples, published papersand their respective tools for everyone who visits their website, except WSDMwhich only offers the download of published papers due to that is a tool that hasproprietary license. In the particular case of UWE and WebML is necessary tomention that in their website they have guided step by step examples to studyand practice the developing of a Web application using their respective supporttool. These two approaches are mostly used in the academic enviroment.Generating conceptual models from requirements (CIM) is an important 2479  Aguilar J.A., Garrigos I., Mazon J.-N., Trujillo J.: An MDA Approach ...
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