Developing Web Applications from Conceptual Models?Vicente Pelechano, Joan Fons, Manoli Albert, and Oscar PastorDepartament of Information Systems and Computation Technical University of Valencia Cami de Vera s/n, E-46022, Spain pele,jjfons,malbert,opastordsic.upv.esAbstract. This paper presents a strategy for the systematic develop- ment of dynamic web applications. The proposal extends an existing OO software production method introducing navigation and presenta- tion expressiveness for applications of this kind. This extensions allow the method going from the problem space to the solution space in a systematic way.1IntroductionIn the last decade, the Web has become the favourite platform for the devel- opment of information systems. The reach is constantly expanding and so are the number and size of the applications, along with the underlying complexity, range of purposes and the time needed to develop and maintain them 1. The development of a Web application is a multifaceted activity, involving not only technical questions, but also organizational, managerial, and even social and artistic issues 2. The term Web Engineering is used to refer to the methods, techniques and tools that have appeared to provide methodological support to undertake the development of applications of this kind. Navigational and presentational modelling is a key point to develop web ap- plications 3. Many approaches have appeared following these main ideas to enrich classic conceptual modelling methods to introduce the new requirements.These approaches also define a systematic method to specify and to develop a full web solution. Some representative examples are OOHDM 4, WebML 5, and UWE 6. These methods combine very well known models (OO and Entity- Relationship models) introducing new models and abstraction primitives to cap- ture the essential expressivity of web applications. The OOWS method introduces two new models to the OO-Method 7, an OO software production method with systematic code generation. These models (navigational and presentational models) allow to specify the inherent charac- teristics of web applications, and they are the input for our web applications generators/compilers.?This work has been partially suported by the CYTED Program, Project VII.18, WEST and the MCYT Project with ref. TIC2001-3530-C02-01.2212OOWS: A Method for Web Conceptual ModellingOOWS (Object Oriented Web Solution) is the extension of the OO-Method 7 that introduces the required expressivity to capture navigational and presenta- tional requirements to develop web applications.It defines a full software development process for the web that comprisestwo major steps: “system specification” and “solution development”. At first,a full specification of the system requirements is built. A strategy oriented to-wards generating the software components that constitute the solution (the finalsoftware product) is defined in the second step.ArchitectureConceptual ModellingImplementationREQUIREMENTS ELICITATION Use Cases and ScenariosStructural ModelDynamic ModelFunctional ModelNavigational ModelPresentational ModelPresentation Tier (WEB Environments (HTML,XML/XSLT)Application Tier(XML WEB Services (Java, .NET, EJB, COM+)Persistence Tier (SQL Server, Oracle)1 23Fig.1. Methodological ApproachThe steps and their associated techniques are the following:1. Conceptual Modelling: conceptual models are built to appropriately cap- ture the requirements of web applications. The modelling tools allow us to specify the functional, navigational and presentation requirements of dy- namic web applications. The modelling process is divided into two steps: (a) functional requirements elicitation. Techniques based on use cases and scenarios are applied to build a conceptual schema (class, sequence and state diagrams are built). An extensive work have been developed in our research group in the OO-Method context 8 See box number 1 in Figure 1. (b) classic conceptual modelling. Using Structural, Functional and Dynamic models, the system structure and behavior is captured (box number 2). (c) navigational and presentational modelling. A navigational model is built in order to capture the navigational requirements. Once the navi-gational model is built, presentation requirements are specified using a presentational model using a set of patterns. These are the extensions that the method introduces to the OO-Method (box number 3). 2. Architectural Design: A multi-tier architectural style is used taking into account the nature of the web services.2223. Implementation: A set of correspondences (transformation rules) between the conceptual abstractions and the software elements that implement eachtier of the architecture are defined, making intensive use of design patterns.3Navigational ModellingThis model allows to capture the navigational semantics of web applications by describing how users would access the system information and functionality. This mo