Engineering accessible Web applications : An Aspect-Oriented approach

Every day more and more users with different abilities and/or temporally or permanent disabilities are accessing the Web, and many of them have difficulties in reaching the desired information. However, the development of this kind of software is complicated for several reasons. Though some of them are technological, the majority are related with the need to compose different and, many times, unrelated design concerns which may be functional as in the case of most of the application’s requirements, or non- functional such as Accessibility. Even though, there is a huge number of tools and proposals to help developers assess Accessibility of Web applications, looking from the designer perspective, there is no such a similar situation. It seems that creating accessible Web sites is more expensive and complicated than creating Web sites and then assessing/modifying them. Although this feeling somehow seems to be true, addressing Accessibility at early design, not only has a significant impact on Web site quality, but also avoids subsequent efforts to return accessible fully developed applications. In this thesis, we present a novel approach to conceive, design and develop Accessible Web applications using concepts from Aspect-Orientation. In order to accomplish our goal, we provide some modelling techniques that we explicitly developed for handling the non-functional, generic and crosscutting characteristics of Accessibility. Specifically, we have enriched the UID technique with integration points to record Accessibility concerns that will be taken into account when designing the user interface. Then, by instantiating the SIG template with association tables, we work on an abstract interface model with Accessibility softgoals to obtain a concrete and accessible interface model for the Web application being developed. We use a real application example to illustrate our ideas and point out the advantages of a clear separation of concerns throughout the development life-cycle. Thus, our proposal is based on recognized design techniques, which we embedded in a software tool, in order to facilitate the transfer of the approach to the industry.Desarrollar aplicaciones Web Accesibles es en la actualidad una necesidad. Cada día más y más usuarios con capacidades diferentes y/o discapacidades temporales o permanentes acceden a la Web, y muchos de ellos tienen dificultades especiales para obtener la información deseada. Sin embargo, el desarrollo de este tipo de software Web es complicado por varias razones. Si bien algunas de estas son de índole tecnológicas, la mayoría están relacionadas con la necesidad de componer intereses de diseño distintos y muchas veces no relacionados entre sí, los cuales a su vez pueden ser funcionales, como lo son la mayoría de los requerimientos específicos de una aplicación, o no-funcionales, como lo es la Accesibilidad. Aún existiendo hoy en día un gran número de herramientas y propuestas para ayudar a los desarrolladores en la evaluación de la Accesibilidad de las aplicaciones Web, la situación no es la misma al observar desde la perspectiva del diseñador Web. Parece ser que diseñar sitios Web accesibles es más costoso y complejo que crear sitios Web y luego evaluarlos/modificarlos. A pesar de que este sentimiento puede ser ciertamente verdadero, los beneficios al modelar la Accesibilidad en etapas tempranas del diseño superan ampliamente las necesidades de un desarrollador al implementar esa Accesibilidad. En esta tesis, presentamos un enfoque original para concebir, diseñar y desarrollar aplicaciones Web Accesibles con una modalidad Orientada a Aspectos. Para alcanzar nuestro objetivo, ofrecemos algunas técnicas de modelado que desarrollamos específicamente para manejar las características no-funcionales, genéricas y transversales de la Accesibilidad como un interés de factor de calidad. Específicamente, enriquecimos los “User Interaction Diagrams” (UIDs) con puntos de integración, los cuales usamos durante el diseño de la interfaz de usuario, para razonar y documentar la Accesibilidad en la actividad de modelado. Luego, instanciando la plantilla del “Softgoal Interdependency Graph” (SIG) con las tablas de asociación, trabajamos en el modelo de interfaz abstracta (compuesta por “ontology widgets”) para obtener un modelo de interfaz concreta y accesible de la aplicación Web en desarrollo. Para ilustrar nuestras ideas y señalar las ventajas de una clara separación de intereses durante el ciclo de vida de desarrollo, utilizamos un ejemplo de aplicación real.Facultad de Informátic

Engineering Accessible Web Applications : An Aspect-Oriented Approach

The development of accessible Web software is complicated for several reasons. Though some of them are technological, the majority are related with the need to compose different and, many times, unrelated design concerns which may be functional as in the case of most of the specific application's requirements, or non-functional such as Accessibility itself. In this paper, we present a novel approach to conceive, design and develop Accessible Web applications in an aspect-oriented manner. In order to reach our goal, we provide some modeling techniques that we specifically developed for handling the non-functional, generic and crosscutting characteristics of the Accessibility concerns. Specifically, we have enriched User Interaction Diagrams with integration points, which are used to reason and document Accessibility for activity modeling during user interface design. Then by instantiating a Softgoal Interdependency Graph template with association tables, we work on an abstract interface model (composed by ontology widgets) to obtain a concrete and accessible interface model for the Web application being developed. We use a real application example to illustrate our ideas and point out the advantages of a clear separation of concerns throughout the development life-cycle.Laboratorio de Investigación y Formación en Informática Avanzad

Towards Adaptable and Adaptive Policy-Free Middleware

We believe that to fully support adaptive distributed applications, middleware must itself be adaptable, adaptive and policy-free. In this paper we present a new language-independent adaptable and adaptive policy framework suitable for integration in a wide variety of middleware systems. This framework facilitates the construction of adaptive distributed applications. The framework addresses adaptability through its ability to represent a wide range of specific middleware policies. Adaptiveness is supported by a rich contextual model, through which an application programmer may control precisely how policies should be selected for any particular interaction with the middleware. A contextual pattern mechanism facilitates the succinct expression of both coarse- and fine-grain policy contexts. Policies may be specified and altered dynamically, and may themselves take account of dynamic conditions. The framework contains no hard-wired policies; instead, all policies can be configured.Comment: Submitted to Dependable and Adaptive Distributed Systems Track, ACM SAC 200

A Peer-to-Peer Middleware Framework for Resilient Persistent Programming

The persistent programming systems of the 1980s offered a programming model that integrated computation and long-term storage. In these systems, reliable applications could be engineered without requiring the programmer to write translation code to manage the transfer of data to and from non-volatile storage. More importantly, it simplified the programmer's conceptual model of an application, and avoided the many coherency problems that result from multiple cached copies of the same information. Although technically innovative, persistent languages were not widely adopted, perhaps due in part to their closed-world model. Each persistent store was located on a single host, and there were no flexible mechanisms for communication or transfer of data between separate stores. Here we re-open the work on persistence and combine it with modern peer-to-peer techniques in order to provide support for orthogonal persistence in resilient and potentially long-running distributed applications. Our vision is of an infrastructure within which an application can be developed and distributed with minimal modification, whereupon the application becomes resilient to certain failure modes. If a node, or the connection to it, fails during execution of the application, the objects are re-instantiated from distributed replicas, without their reference holders being aware of the failure. Furthermore, we believe that this can be achieved within a spectrum of application programmer intervention, ranging from minimal to totally prescriptive, as desired. The same mechanisms encompass an orthogonally persistent programming model. We outline our approach to implementing this vision, and describe current progress.Comment: Submitted to EuroSys 200

Knowledge infrastructures for software service architectures

Software development has become a distributed, collaborative process based on the assembly of off-the-shelf and purpose-built components or services. The selection of software services from service repositories and their integration into software system architectures, but also the development of services for these repositories requires an accessible information infrastructure that allows the description and comparison of these services. General knowledge relating to software development is equally important in this context as knowledge concerning the application domain of the software. Both form two pillars on which the structural and behavioural properties of software services can be addressed. We investigate how this information space for software services can be organized. Focal point are ontologies that, in addition to the usual static view on knowledge, also intrinsically addresses the dynamics, i.e. the behaviour of software. We relate our discussion to the Web context, looking at the Web Services Framework and the Semantic Web as the knowledge representation framework

Data integration through service-based mediation for web-enabled information systems

The Web and its underlying platform technologies have often been used to integrate existing software and information systems. Traditional techniques for data representation and transformations between documents are not sufficient to support a flexible and maintainable data integration solution that meets the requirements of modern complex Web-enabled software and information systems. The difficulty arises from the high degree of complexity of data structures, for example in business and technology applications, and from the constant change of data and its representation. In the Web context, where the Web platform is used to integrate different organisations or software systems, additionally the problem of heterogeneity arises. We introduce a specific data integration solution for Web applications such as Web-enabled information systems. Our contribution is an integration technology framework for Web-enabled information systems comprising, firstly, a data integration technique based on the declarative specification of transformation rules and the construction of connectors that handle the integration and, secondly, a mediator architecture based on information services and the constructed connectors to handle the integration process

Towards a re-engineering method for web services architectures

Recent developments in Web technologies – in particular through the Web services framework – have greatly enhanced the flexible and interoperable implementation of service-oriented software architectures. Many older Web-based and other distributed software systems will be re-engineered to a Web services-oriented platform. Using an advanced e-learning system as our case study, we investigate central aspects of a re-engineering approach for the Web services platform. Since our aim is to provide components of the legacy system also as services in the new platform, re-engineering to suit the new development paradigm is as important as re-engineering to suit the new architectural requirements

A survey of QoS-aware web service composition techniques

Web service composition can be briefly described as the process of aggregating services with disparate functionalities into a new composite service in order to meet increasingly complex needs of users. Service composition process has been accurate on dealing with services having disparate functionalities, however, over the years the number of web services in particular that exhibit similar functionalities and varying Quality of Service (QoS) has significantly increased. As such, the problem becomes how to select appropriate web services such that the QoS of the resulting composite service is maximized or, in some cases, minimized. This constitutes an NP-hard problem as it is complicated and difficult to solve. In this paper, a discussion of concepts of web service composition and a holistic review of current service composition techniques proposed in literature is presented. Our review spans several publications in the field that can serve as a road map for future research