Survey of Existing Web Models Techniques to Design Web Application

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1 Survey of Existing Web Models Techniques to Design Web Application Paras Patel 1, Anup Hande 2 and Dr. B. B. Meshram 3 1 Computer Engineering & Information Technology, Veermata Jijabai Technological Institute, Mumbai, Maharashtra , India parasprince2001@gmail.com 2 Computer Engineering & Information Technology, Veermata Jijabai Technological Institute, Mumbai, Maharashtra , India handeanup@gmail.com 3 Computer Engineering & Information Technology, Veermata Jijabai Technological Institute, Mumbai, Maharashtra , India bbmeshram@vjti.co.in ABSTRACT Over the last few years, the web is establishing increased importance in entire world with the rise of social networking sites and the semantic web, facilitated and driven by the popularity of client-side scripting commonly known as AJAX. These allow extended functionality and more inter in web applications. Engineering practices dictate that we need to be able to model these applications. However, languages to model web applications have fallen behind, with most existing web modeling languages still solely focused on the hypertext structure of web sites, with little regard for user interaction or common web-specific concepts. This article surveys Model-driven web engineering methods in a comparative study and analyzes the techniques proposed for specifying functional, data and navigational requirements as well as the mechanisms provided for automatically translating these requirements into conceptual models. Our main goal is to provide a critical view of the support that is provided by these methods for handling web application requirements in order to show their current limitations and strengths. We present a brief survey of existing web modeling languages including WebML, UWE, W2000 and OOWS, along with a discussion of their capability to describe these new modeling approaches. Finally, we discuss the possibilities of extending an existing language to handle these new concepts. Keywords: Web engineering, Requirements engineering, modeldriven development, web models, inter, AJAX Introduction Web modeling (model-driven Web Development) is a branch of Web engineering which addresses the specific issues related to design and development of large-scale Web applications[2]. It focuses on the design notations and visual languages that can be used for the realization of robust, well-structured, usable and maintainable Web applications.designing a data-intensive Web site amounts to specifying its characteristics in terms of various orthogonal abstractions. 1.1 Why do we need modeling? To Define an abstract view of a real-world entity, To Finding & discovering objects/concepts in a domain and To Assigning responsibilities to objects. Tool of thought are: To Reduce complexity and Document design decisions. 1.2 Software Application Modeling [3] Levels It includes the how & what of an application. That means Application Logic and User Interface of Application. In turn, when modeling the presentation level, the focus is on a uniform presentation structure for the pages to achieve a brand recognition effect for the Web application among its users. Although the visual appearance of a Web application is of importance, aesthetic aspects are not within the major focus of modeling Aspects - basically two types Structural (objects, attributes & relationships) Behavior (function and processes) Following the object-oriented principles, structure and behavior are modeled at each of the three levels, i.e. at content, hypertext and presentation. The relevance of the structure and behavior models depends on the type of Web application to be implemented. Web applications which make mainly static information available require less behavior modeling compared with highly interactive Web applications, such as for example e-commerce applications which provide search engines, purchase order functions, etc. With respect to mapping the different levels, it is recommended to use a uniform modeling formalism for structure and behavior, which might allow relying on one single CASE tool. Naturally, this modeling formalism has to cope with the specific characteristics of each of the three levels. 514

2 Figure 2 Web Application Model Figure 1 Software Application Model [3] Phases - Development Cycle Analysis Design Implementation The sequence of steps to model the levels should be decided by the modeler. Depending on the type of Web application, it should be possible to pursue an informationdriven approach, i.e., starting with content modeling, or a presentation-driven approach, i.e., starting with modeling of the application s presentation aspects. Model-based development in Web engineering contradicts somewhat the often found practices in Web projects comprising, e.g., short-lived development cycles and the desire for agile methods. A model-based approach counters this situation with a comprehensive specification of a solution model and, if appropriate case tool support is available, the possibility to automatically generate the (prototypical) Web application. Models also ensure the sustainability of solution ideas, in contrast to shorter-lived software solutions. In addition, the communication amongst the developers of a team as well as between customers and developers is improved Phases Approach depends upon type of application Information based: Document-centric Web sites, which are hierarchical collections of static HTML documents (basically, plain text and images) that offer read-only information based on a set of structured content, navigation patterns, and presentation characteristics designed and stored a priori. Presentation based: Presentation based that refers to the visual elements that comprise the Web pages. Logic based o Business Logic: Means changes in the underlying platform do not affect existing applications. o Application Logic: Means business logic can evolve independently from the underlying technology. Analysis and Design of Web Applications [4] 1.3 Web Application Modeling [3] Levels It contains Information, Node/link structure, UI and page layout separate. Presentation Structure : user interface elements and their composition Behavior : reactions to input events, interaction and synchronization between user interface elements Hypertext Structure: page compositions and navigational relationships Behavior: run-time behavior of hypertext Content Structure: domain-dependent data Behavior: domain-dependent application logic Figure 3 Analysis and Design of Web Application Model Analysis Phase : Requirement Specification of Web Application Design Phase: It contains Representation of the software to be built which is either Technology dependent or Technology independent. Implementation Phase: It consist of Executable models and Executable codes are buit up here Aspects Same as above Software Applications Customization Context information Methods adopted or the webs are not new. They are derived from traditional SW. But Question is that Why hyperlinks? Why adding a new layer? So, we can say Corresponds to the status of web 515

3 applications and Improve reuse Content, is the content as displayed in the web application equivalent to information structure. In web application several pages access the same content. If you model it you can reuse it. In short modeling is a technique used in analysis and design. It uses notation (syntax) (graphical representation and language), process for building models (rules and guidelines) and Graphical editors. Which have Object- Oriented Analysis & Design. Analysis: Finding & discovering classes of objects/ concepts in a domain Design: Defining software objects & how they interact to fulfill requirements. 3 MODEL DRIVEN DEVELOPMENT 3.2 Introduction When it comes down to it, the real point of software development is cutting code. Diagrams are, after all, just pretty pictures. No user is going to thank you for pretty pictures. 3.3 Unified Modelling Language (UML)[8] The Unified Modeling Language is a visual language for specifying and documenting the artifacts of systems. It is Language of choice (and ISO standard) for diagramming notation in OO development. Structural Class diagrams (domain models) [4] Behavioral Use Cases [7], Sequence diagrams [7] Currently at version 2.0, although many analysts and designers still use The Role of Model in the Development 1) Models as sketch : It has been developed to For communicating ideas and alternatives. It s essence is selectivity although sketchers don t have to care much about it. 2) Models as blueprint : All design decisions (maybe of a particular area) are laid out. It s essence is Completeness programming should be pretty straightforward. But some time there is a Issue of reverse engineering. 3) Models as program: we can generate application automatically. In MDA separation of Platform Independent Model (PIM) and Platform Specific Model (PSM) [4].ideally the transformation is "parameterized" by a Platform Description Model (PDM) it s essence is models become the source code. 3.5 Model - Code Interplay Error! Reference source not found. Figure 4 Model Code Interplay Systematic development on basis of models and now a days Models become the first hand artifacts in the software or web development cycle. Key concepts are abstraction from implementation detail and systematic transformations. Related Terminology are as below: Model Driven [Software] Engineering (MDE), Model Driven [Software] Development (MDD/MDSD), Model Driven Architecture (MDA) Model Driven Web Engineering (MDWE) 4 DEVELOPMENT IN THE MDA 4.2 PIM : Platform Independent Model(PIM) represents business functionality and behavior without technology details 4.3 PSM Applies a standard mapping to create or generate a Platform Specific Model (PSM) from the PIM 4.4 Code Model Create or generate the code for PSM Figure 5 Development Model in MDA[4] Due to short development cycles and the complexity of Web applications, it is recommended to use tools that support not only the modeling itself, but also and particula rly automatic code generation and model consistency check. The following subsections describe WebRatio Site Development Studio, VisualWADE, and 516

4 the OpenUWE Suite as examples for this type of tools. 5 STEPS FOR DEVELOPMENT 4.1 Step-1 All MDA development projects start with the creation of a Platform Independent Model (PIM), which is expressed in UML. The PIM expresses only business functionality and behavior. Built by business and modeling experts working together, this model expresses business rules and functionality undistorted, as much as possible, by technology. The clarity of this modeling environment allows business experts to ascertain, much better than they could if working with a technological model or application that the business functionality embodied in the PIM is complete and correct. Another benefit: Because of its technological independence, the PIM retains its full value over the years, requiring change only when business conditions mandate. Transition: MDA tool applies a standard mapping to generate Platform-Specific Model (PSM) from the PIM. Code is partially automatic & partially handwritten. 4.2 Step-2 Once the first iteration of the PIM is complete, it is stored in a MOF based Repository and input to the mapping step which will produce a Platform-Specific Model (PSM). To produce your PSM, you will have to select a target platform or platforms for the modules of your application. Such as J2EE,.NET etc. Transition: MDA Tool generates all or most of the implementation code for deployment technology selected by the developer. 4.3 Step-3 Once the PSM has been created/generated, the 3rd and final step is to generate the code/implementation model. This will create/generate all of the files the platform requires. When I talk about platforms, I m referring to the application server(s) your application will run on and programming languages, such as Java, C++ or C# your application will be generated into. This will result in a first cut working application, which can be further enhanced through the MDA process or by hand-coding 4.4 Step-4 Take note that the mapping standard between PIM, PSM and the Code Model has been defined by OMG but the implementation not. MDA compliant tool vendors have implemented portions of the MDA, but Optimal is one of the few tools that has implemented the MDA completely to automatically generate a complete application from a PIM to PSM and finally to the Code Model. 6 MODELLING METHOD HISTORY ERROR! REFERENCE SOURCE NOT FOUND. Figure 6 Modelling method History Diagram Modeling methods have different paradigms, depending on their origin & focus: Data-oriented methods originate from the field of database systems; they are mainly based on the ER model enhanced by specific concepts for modeling on the hypertext level. The primary focus of these methods is the modeling of database-driven Web applications. Examples of data-oriented methods include the Relationship Management Methodology(RMM),Hera and the Web Modeling Language. Hypertext-oriented methods center on the hypertext character of Web applications; they emerged mainly from the field of hypertext systems. Representatives of this group are the Hypertext Design Model (HDM), which has been extended intow2000, and HDM-lite, or the Web Site Design Method (WSDM). Object-oriented methods are based on either OMT (for the very early methods) or UML. UML is the preferred notation when a standard language for modeling is selected. This category includes the Object-Oriented Hypermedia Design Method (OOHDM) (Schwabe and Rossi 1998), UML-based Web Engineering (UWE) Object-Oriented Web Solutions (OOWS) and the Object-Oriented Hypermedia (OO-H) method. Software-oriented methods look at Web applications mainly from the perspective of traditional software development, using techniques that strongly follow classical Software Engineering. 7 WEBML (WEB MODELLING LANGUAGE) 7.2 Introduction WebML enables designers to express the core features of a site at a high level, without committing to detailed architectural details. WebML concepts are associated with an intuitive graphic representation, which can be easily supported by CASE tools and effectively communicated to the non-technical members of the site development team. 7.3 Architecture of WebMLError! Reference source not found. WebML is a third-generation Web design methodology base on MDA. It is a conceptual language aimed at 517

5 supporting all the activities and perspectives of Web applications design, especially data-intensive and processcentric web application. According to the MVC framework, WebML model is divided into Data Model, Hypertext Model and Presentation Model. Figure 1 shows the architecture of the WebML. The Data Model describes the conceptual data organization according to the Entity-Relationship Model. The Hypertext Model enables the specification of the front-end of web applications. The Presentation Model extends the hypertext model with simple constructs such as operations and transactions, enabling the invocation of predefined operations. 8.3 UML Class Diagram UML class diagrams used at analysis-level and designlevel in which elements to be modeled represented by classes Units of information, users of the system (user model), associations represent relationships between classes, aggregation used to show an whole/part relationship, Composition is a strong form of aggregation that requires a part instance be included in at most one composite at a time. If a composite is deleted, all of its parts are normally deleted with it. And inheritance used to show hierarchies between classes. In addition to the class diagram, Figure 4-1 shows a state machine diagram used to model the various states of a paper in the reviewing system. It shows that a submitted paper will be assigned to three reviewers for review after the submission deadline has expired. If a pre-set threshold value is reached, the paper is accepted; otherwise, it is rejected. In both cases the authors are noticed via about the outcome of the review. Finally, an accepted paper will be printed once final version has been submitted. 8.4 Content Behaviour Model [4] Figure 7 WebML Architecture Diagram 8 CONTENT MODELLING 8.2 Introduction To model the information requirements of a Web application Diagramming the structural (i.e., information objects) and Behavioral aspects of the information. It expresses the data content of the site, in terms of the relevant Entities and relationships. It doesn t concerned with navigation. And Primary Models are Class diagrams (enough for static applications), State machine diagrams (captures dynamic aspects) and ER- diagrams. Although Representation with pure UML is sufficient stereotypes are not needed. The information provided by a Web application is one of the most important factors for the success of that application, not least due to the origins of the Web as an information medium. Modeling the content in the sense of pure data modeling is normally sufficient for static Web applications. Complex Web applications additionally require the modeling of behavioral aspects. This means that content modeling includes the creation of the problem domain model, consisting of static and dynamic aspects, as known from traditional Software Engineering. Figure 8 Content Behavior Model Activity Diagram 8.5 Comparison of Object Operations between WebML and OO-H[1]. Figure 9 Comparison of WebML & OO-H Figure (a) shows an excerpt of the content model of the album store example. In Figure (b) we depict the corresponding OO-H content model that needs to be generated by the transformation rules. For each Entity in the content model of WebML an OO-H Class is generated. 518

6 9 HYPERTEXT MODELLING Besides transforming the Entities Attributes, in OO-H the Constructor(), Destructor(), and Modifier() operations must be defined for the Class as well. Likewise for each Relationship of an Entity the Relationer() and Unrelationer() operations have to be generated for the corresponding Class in the OO-H content model. 8.6 Content Structure Model [4] Figure 10 Content Structure Model Class Diagram [4] 9.2 Introduction Its purpose is to model the navigation paths available to users major UWE Artifacts[8] are Hypertext Structure Model which navigating among classes, Access Model which UML-compliant site map, Focuses on the structure of the hypertext & access elements Use <<navigation class>>> annotation to distinguish from content classes and it is based on content models main goals are to represent nodes and links of the hypertext structure, to design navigation paths, and to avoid disorientation and cognitive overload. Resultant we get navigation model which represented by a UML class diagram it uses specific modeling elements for Web concepts and Modeling elements are basic elements and access primitives. There are some other methodologies also available own notation for hypertext elements. Different diagram types are UML state diagram or own diagram type. The non-linearity of hypertext is one of the most important properties to be taken into account when modeling Web applications. Thus the hypertext structure has to be designed carefully. This can be achieved by using suitable access structures, i.e., navigation options, to avoid the risk of users getting lost and putting them under excessive cognitive stress. 9.3 Different Types of Links [4] HDM (Hypertext Design Model) Structural links connect elements of the same node, Perspective links put various views of a node in relation to each other. Application links put different nodes in relation to each other, depending on the application WebML (Web Modeling Language) Contextual links carry context information, Non-contextual links have no associated context information. Intra-page links are used when the source and the destination of a link belong to the same page. Inter-page links are used when the source and the destination are on different pages. Based on the functional requirements of Web applications, the UWE modeling method defines the following types of links: Navigation links are used to navigate between nodes, Process links point to the start node of a process. External links point to a node not directly belonging to the application The OO-H (Object-Oriented Hypermedia) modeling method defines five types of links as follows: I-links (internal links) point to nodes inside the boundaries of a given navigational requirement. T-links (traversal links) point to nodes covering other navigational requirements. R-links (requirement links) point to a start of a navigational path. X-links (external links) point to external nodes. 519

7 S-links (service links) point (with their corresponding response links) to services HDM Structural links connect elements of the same node, Perspective links put various views of a node in relation to each other and Application links put different nodes in relation to each other, depending on the application WebML In Contextual links carry context information. Noncontextual links have no associated context information. With regard to the distribution of nodes on the hypertext level over pages on the presentation, Intra-page links are used when the source and the destination of a link belong to the same, and Inter-page links are used when the source and the destination are on different pages. 9.4 Navigation Access Model [4] In Hypertext structure models describe navigation, but not orientation. Access models describe both through Navigation patterns, used to consistently describe conventional elements. <<index>> (list of objects of the same type) <<menu>> (list of heterogeneous objects) <<guided-tour>> (sequential links) <<query>> The hypertext structure model built so far alone is not sufficient to describe how nodes can be reached by navigation. To allow users to navigate to nodes the users need navigation and orientation aids. These are formulated in the form of access structures refining the hypertext structure model. Recurring access structures are described in as design patterns, also called hypermedia design patterns or navigation patterns. The use of these navigation patterns helps to increase the quality of the hypertext model tremendously. Figure 11 Navigation Acess Model for online PC shop 10 COMPARISON AND ANALYSIS 10.1 Comparison of Existing Language to model Web site Features WebML UWE W2000 OOWS OOHD M Events Ok - Poor - - Broswer Control Lifecycles Users Security Databases Messaging UI Modelling Platform Independent Standards Meta-models Model Verification CASE Tool Poor Poor Good - - Good Poor Poor Poor - Ok Ok Poor - - Good Ok Poor Poor Poor Good Poor Ok - - Poor Ok Ok Poor Ok Excellent Excellent Good Excellen t Good Poor Excellent Excellent Ok Poor Poor Excellent Excellent Poor - Ok Ok Good Ok Poor Ok - Figure 12 Feature Comparison of Existing Language to model Web site 10.2 Summary of the Requirements Specification Perspective Analysis Method Functional Req. Data Req. Navigational Req. OOHDM Use cases, - UIDs textual templates WSDM Natural language task diagram Natural language Natural language task diagram SOHDM Scope diagram, - - SACs UWE Web process use cases, stereotyped diagrams, use - Navigation use cases, stereotyped diagrams cases WebML User templates, diagrams, use Data dictionary Site specification templates cases OOH Use cases - Web requirements metamodel(we- RMExt) OOWS W2000 NDT Task characterization templates, diagrams Functional use cases Use cases formatted templates Information templates Task taxonomy, diagrams - Navigational use cases Formatted Formatted templates templates Figure 13 Summary of the Requirements Specification Perspective Analysis 520

8 10.3 Summary of the MDD Perspective Analysis Method Visual Syn. And Meta Model Req. Spec. Tool OOHDM Ok - WSDM Ok - - SOHDM Ok - - UWE Ok AgroUWE Magic UWE WebML Ok - OOH Ok - - OOWS Ok RE tools based on Eclips W2000 Ok - - NDT Ok NDT suits Deriv. of Conceptual Models specified with : textual guidelines applied : manually (no tools) specified with: QVT applied: manually (no tools) specified in : textual guidelines applied : manually(no lools) specified with: graph transformations applied : automatically (AGG tools) Implemented as AGG Graph Transformation Specified with :: QVT Applied: automatically (NDT Suite) Implemented as: Enterprise Architect templates. Figure 14 Summary of the MDD Perspective Analysis 11 ACKNOWLEDGMENT A large number of different methods for Web application modeling have been developed in the last decade. However, some methods will probably converge during the course of further development. It is currently hard to predict how far this converging trend will go and whether it will eventually lead to a Unified Web Modeling Language, similarly to the development of the UML. It is, however, uncontested that there is a trend towards using UML as notation language. Some methods are moving from their proprietary notation to a UML compliant one and introduce a UML profile for their method. The methods that will succeed will be determined by the tool support offered for their modeling method. In the future, tools will systematically support not only the notation, but also the development process allowing for a model-driven development approach. However, this means that the methods will have to define clear guidelines and approaches, in contrast to the current situation. It also means that agile approaches (Ambler 2002) will most likely have to be considered, but they will have to be harmonized in view of (semi) automatic generation. The inclusion of Web services in model-based Web application development projects will bring new challenges, the most critical probably being the interplay between top-down modelling and bottom-up integration of existing services and adequate tool support. References [1] Manuel Wimmer, Andrea Schauerhuber, Wieland Schwinger, Horst Kargl : On the Integration of Web Modeling Languages: Preliminary Results and Future Challenges :IEEE TRANSACTIONS ON SOFTWARE ENGINEERING. [2] Guotao Zhuang, Junwei Du : MDA-BASED Modeling and Implementation of E-Commerce Web Applications in WebML 2nd international workshop on computer CSE 2009 [3] Gerti Kappel, Birgid Pröll, Siegfried Reich, Werner Retschitzegger (eds.),dpunkt-verlag: Web Engineering: Systematic Development of Web Applications [4] Gustavo Rossi, Oscar Pastro, Daniel Schwade, Luis Olsina Web Engineering: Modelling and Implementing Web Applications Human- Computer Interaction Series ISSN [5] Stefano Ceri, Piero Fraternali, Aldo Bongio : Web Modeling Language (WebML): a modeling language for designing Web sites IETJournal [6] Andreas Kraus : Model Driven Software Engineering for Web Applications" [7] Nathalie Moreno, Piero Fraternali, Antonio Vallecillo WebML Modeling in UML IET Journal. [8] Marco Brambilla, Sara Comai, Piero Fraternali, Maristella Matera: "DESIGNING WEB APPLICATIONS WITH WEBML AND WEBRATIO" [9] Stefano Ceri, Piero Fraternali, Maristella Matera :"Conceptual modeling of data-intensive Web applications [10] Thiago Jabur Bittar, renata P. M. Fortes, Luanana Lopes Lobato, and Willian M. Watanabe "Web Communication and Interaction Modeling using Model Driven Develpment SIGDOC 09, October 5 7, 2009, Bloomington, Indiana, USA 521