Martin Gaedke

Discovering and Maintaining Links on the Web of Data

The Web of Data is built upon two simple ideas: Employ the RDF data model to publish structured data on the Web and to create explicit data links between entities within different data sources. This paper presents the Silk --- Linking Framework, a toolkit for discovering and maintaining data links between Web data sources. Silk consists of three components: 1. A link discovery engine, which computes links between data sources based on a declarative specification of the conditions that entities must fulfill in order to be interlinked; 2. A tool for evaluating the generated data links in order to fine-tune the linking specification; 3. A protocol for maintaining data links between continuously changing data sources. The protocol allows data sources to exchange both linksets as well as detailed change information and enables continuous link recomputation. The interplay of all the components is demonstrated within a life science use case.

Object-oriented Web application development

Most Web applications are still developed ad hoc. One reason is the gap between established software design concepts and the low-level Web implementation model. We summarize work on WebComposition, a model for Web application development, then introduce the WebComposition Markup Language, an XML-based language that implements the model. WCML embodies object-oriented principles such as modularity, abstraction and encapsulation.

WebComposition: an object-oriented support system for the Web engineering lifecycle

Maintenance of web applications is a difficult and error-prone task because many design decisions are not directly accessible at run time, but rather embedded in file-based resources. In this paper we introduce the WebComposition system addressing this problem. This system is based on a fine-grained object-oriented web application model, and maintains access to it throughout the lifecycle for management and maintenance activities. Modifications of the model are made effective in the web by incrementally mapping the model to file-based resources.

A modeling approach to federated identity and access management

As the Web is increasingly used as a platform for heterogeneous applications, we are faced with new requirements to authentication, authorization and identity management. Modern architectures have to control access not only to single, isolated systems, but to whole business-spanning federations of applications and services. This task is complicated by the diversity of todays specifications concerning e.g. privacy, system integrity and distribution in the web. As an approach to such problems, in this paper, we introduce a solution catalogue of reusable building blocks for Identity and Access Management (IAM). The concepts of these blocks have been realized in a configurable system that supports IAM solutions for Web-based applications.

Web Content Delivery to Heterogeneous Mobile Platforms

It is widely acknowledged that information such as web content should be adapted for mobile platforms to account for restrictions in mobile environments. As emerging mobile platforms such as different kinds of Personal Digital Assistant (PDA) tend to vary largely in their capabilities, we suggest that adaptation should be platform-specific. Common approaches for content adaptation are automated conversion and explicit specification of adapted content, with a trade-off between quality and development/maintenance effort. As alternative avoiding this trade-off, we propose a simple object-oriented framework for content adaptation. To facilitate the use of this framework in the Web, we base our approach on the object-oriented WebComposition model and its XML-based implementation WCML. We apply our object-oriented approach to an example application to demonstrate how object-oriented specification of platform-adapted content reduces development/maintenance effort.

Development and Evolution of Web-Applications Using the WebComposition Process Model

From a software engineering perspective the World Wide Web is a new application platform. The implementation model that the Web is based on makes it difficult to apply classic process models to the development and even more the evolution of Web-applications. Component-based software development seems to be a promising approach for addressing key requirements of the very dynamic field of Web-application development and evolution. But such an approach requires dedicated support. The WebComposition Process Model addresses this requirement by describing the component-based development of Web-applications. It uses an XML-based markup language to seamlessly integrate with existing Web-standards. For the coordination of components the concept of an open process model with an explicit support for reuse is introduced. By describing application domains using domain-components the process model addresses the need for a controlled evolution of Web applications.

Exploiting single-user web applications for shared editing: a generic transformation approach

In the light of the Web 2.0 movement, web-based collaboration tools such as Google Docs have become mainstream and in the meantime serve millions of users. Apart from established collaborative web applications, numerous web editors lack multi-user support even though they are suitable for collaborative work. Enhancing these single-user editors with shared editing capabilities is a costly endeavor since the implementation of a collaboration infrastructure (accommodating conflict resolution, document synchronization, etc.) is required. In this paper, we present a generic transformation approach capable of converting single-user web editors into multi-user editors. Since our approach only requires the configuration of a generic collaboration infrastructure (GCI), the effort to inject shared editing support is significantly reduced in contrast to conventional implementation approaches neglecting reuse. We also report on experimental results of a user study showing that converted editors meet user requirements with respect to software and collaboration qualities. Moreover, we define the characteristics that editors must adhere to in order to leverage the GCI.

Mockup-Driven Development: Providing agile support for Model-Driven Web Engineering

Context: Agile software development approaches are currently becoming the industry standard for Web Application development. On the other hand, Model-Driven Web Engineering (MDWE) methodologies are known to improve productivity when building this kind of applications. However, current MDWE methodologies tend to ignore important aspects of Web Applications development supported by agile processes, such as constant customer feedback or early design of user interfaces. Objective: In this paper we analyze the difficulties of supporting agile features in MDWE methodologies. Then, we propose an approach that eases the incorporation of well-known agile practices to MDWE. Method: We propose using User Interface prototypes (usually known as mockups) as a way to start the modeling process in the context of a mixed agile-MDWE process. To assist this process, we defined a lightweight metamodel that allows modeling features over mockups, interacting with end-users and generating MDWE models. Then, we conducted a statistical evaluation of both approaches (traditional vs. mockup-based modeling). Results: First we comment on how agile features can be added to MDWE processes using mockups. Then, we show by means of a quantitative study that the proposed approach is faster, less error-prone and still as complete as traditional MDWE processes. Conclusion: The use of mockups to guide the MDWE process helps in the reduction of the development cycle as well as in the incorporation of agile practices in the model-driven workflow. Complete MDWE models can be built and generated by using lightweight modeling over User Interface mockups, and this process suggests being more efficient, in terms of errors and effort, than traditional modeling in MDWE.

End-user-oriented telco mashups: the OMELETTE approach

With the success of Web 2.0 we are witnessing a growing number of services and APIs exposed by Telecom, IT and content providers. Targeting the Web community and, in particular, Web application developers, service providers expose capabilities of their infrastructures and applications in order to open new markets and to reach new customer groups. However, due to the complexity of the underlying technologies, the last step, i.e., the consumption and integration of the offered services, is a non-trivial and time-consuming task that is still a prerogative of expert developers. Although many approaches to lower the entry barriers for end users exist, little success has been achieved so far. In this paper, we introduce the OMELETTE project and show how it addresses end-user-oriented telco mashup development. We present the goals of the project, describe its contributions, summarize current results, and describe current and future work.

Supporting compositional reuse in component-based Web engineering

The World Wide Web’s anticipated scope as an environment for knowledge exchange has changed dramatically. Without major modifications to its primary mechanisms the Web has turned into a platform for distributed applications. The originally simple and well-defined coarse-grained implementation model of the Web now hinders Web application development. Fine-grained development artifacts, design patterns, and other well-established Software Engineering methods are hard to reuse in the Web after they have found their way into implementation resources. The application of Software Engineering practice to development for the Web, which is also referred to as Web Engineering, and especially the systematic reuse of components for Web-application development at low-costs is a main goal to achieve. This paper explains how the object-oriented and component-based WebComposition Markup Language (WCML) addresses these problems. A systematic approach to code reuse is presented with the WebComposition Repository, which is an essential tool for retrieval and classification of large component sets. The Repository’s architecture is crafted to support multiple representation and classification approaches. It facilitates reuse in component-based Web Engineering.