The increasing complexity of web-based systems necessitates intuitive, specialised modelling tools. The WebComposition Architecture Model (WAM) provides a formal notation for modelling web systems across organisational boundaries, with explicit support for federation and modelling of trust relationships. However, to date, WAM lacks dedicated tool support, forcing software architects to use general-purpose diagramming tools, which can be challenging and complex. This paper presents WAMflow, a web-based diagram editor designed explicitly for supporting the creation and editing of WAM diagrams. The editor enables Web Engineers to visually design federated web architectures in the browser and allows to export diagrams for sharing and documentation purposes. In a usability study based on the User Experience Questionnaire (UEQ) we observed high attractiveness, efficiency, and clarity ratings. Participants’ qualitative feedback provided valuable additional insights from which we derive directions for future improvements in this paper.

AI components are increasingly integrated into complex web systems, especially in the context of AI-as-a-Service. However, trustworthiness of the resulting architectures is jeopardized by AI biases in the models used, the data they were trained on, or the way they are deployed. This problem needs to be addressed by systematic approaches of managing the AI bias-related risks. We propose AIBDB, an infrastructure inspired by the Common Vulnerabilities and Exposures (CVE) system that serves as a knowledge base about known AI biases and supports software architects in automatically identifying architectural risks of AI bias. With the first proof-of-concept implementation of this web-based AI bias management infrastructure, we conducted a qualitative user study yielding feedback from 7 participants through thematic analysis of their 112 responses on the usability, usefulness and suggestions for improvement. We contribute to the development of future fair and unbiased AI-driven solutions in the web in the context of the ongoing research on Trustworthy and Human-centric AI and the increasing importance for organizations to address AI bias through recent regulations.

In today’s data-driven world, people are increasingly prioritising data privacy and control. This awareness has sparked an initiative for a decentralized web, where web applications no longer rely on centralized data storage. Solid, a prominent approach for a decentralized web, allows users to store their data in decentralized pods of their control. However, the integration of data from various and potentially untrusted sources can lead to malicious or harmful results and impair user experience. To solve this problem for social networks, we propose a trust-aware and decentralized web application called TrADS. It utilises the MVC pattern to integrate external data from Solid pods based on trust evaluations. In this article, we extend our first paper on TrADS with further details on related work assessment, concept and implementation. We are also extending our evaluation to a second international user study with another 64 participants. We measure the user experience instead of pure usability and form two separate groups of participants, one of which experiences the trust awareness of TrADS and one of which does not. The results do not yet show significant improvement in the user experience but show that after using trust awareness in a social network, users favour a network with such features.

Application logic is inherently distributed between client and server due to the fundamental Client/Server architecture of the Web. The individual distribution is specified at design time and remains unchanged stable, preventing individual load distribution between clients and server at runtime. Dynamic code mobility at runtime, in contrast, allows to balance the needs of users, through increased responsiveness, and software providers, through better resource usage and cost reductions. Enabled by WebAssembly, the Web ecosystem recently provides the technological foundation for relocating code units during runtime. However, leveraging these capabilities to enhance web applications with dynamic code migration presents challenges for web engineers. In response, we propose an innovative distributed Client/Server software architecture for web applications. This architecture facilitates the dynamic migration of code at runtime, and addresses the technical challenges like dependency management, control and data flow distribution, communication, and interfaces. This novel software architecture serves as a reference for web engineers aiming to enrich their web applications with dynamic code mobility. Additionally, it contributes to the ongoing reevaluation of the Web ecosystem in light of the widespread adoption and standardization of WebAssembly across major browsers. Through experimentation in four scenarios, we demonstrate the feasibility of implementing this architecture, its negligible impact on performance and the optimization potential for individual code distributions across client and server.

Indoor Navigation Systems are constantly improved in a variety of technological fields, but often without considering individual user requirements. As a direct consequence, navigation information is not sufficient for the variety of all users. By combining and evaluating user requirements and data models for indoor representation, five categories of indoor navigation information were compiled. OpenStreetMap (OSM) serves as a basis to form items for an online survey for able-bodied, visually and motorically impaired people. Based on the results, we determined: User groups are an important element in indoor navigation. Individual preferences and time dependence of information need to be considered additionally. These results are then used to derive implications for several stages and components in the technological development process. We argue that following these implications by including user requirements in these processes will lead to a higher satisfaction with Indoor Navigation Systems for all users.

Enabling end users to take a proactive role in the development of Web of Things (WoT) applications that achieves their goals is a challenge for End User Development (EUD) in the context of WoT. This can be achieved through Artificial Intelligence (AI) planning algorithms if the relevant WoT concepts and relationships are described in an interoperable way. Although similar, existing service description languages like WSDL or ontologies like OWL-S are not sufficient to represent all required characteristics of concrete WoT planning scenarios. To address these limitations, in this paper we present the Web of Things Description Language (WoTDL) ontology which is an extension of existing WoT models to describe the key concepts of AI planning for automatic WoT composition. To demonstrate the feasibility of our approach, we follow the best practices recommended by the semantic web community and describe the physical devices of our smart home testbed in an AI planning scenario using WoTDL.

The Internet of Things (IoT) primary objective is to make a hyper-connected world for various application domains. However, IoT suffers from a lack of interoperability leading to a substantial threat to the predicted economic value. Schema.org provides semantic interoperability to structure heterogeneous data on the Web. An extension of this vocabulary for the IoT domain (iot.schema.org) is an ongoing research effort to address semantic interoperability for the Web of Things (WoT). To design this vocabulary, a central challenge is to identify the main topics (concepts and properties) automatically from existing knowledge in IoT applications. We designed KE4WoT (Knowledge Extraction for the Web of Things) to automatically identify the most important topics from literature ontologies of 3 different IoT application domains - smart home, smart city and smart weather - based on our corpus consisting of 4500 full-text conference and journal articles to utilize domain-specific knowledge encoded within IoT publications. Despite the importance of automatically identifying the relevant topics for iot.schema.org, up to know there is no study dealing with this issue. To evaluate the extracted topics, we compare the descriptiveness of these topics for the 10 most popular ontologies in the 3 domains with empirical evaluations of 23 domain experts. The results illustrate that the identified main topics of IoT ontologies can be used to sufficiently describe existing ontologies as keywords.

Metric-based assessment of web user interface (WUI) quality attributes is shifting from code (HTML/CSS) analysis to mining webpages'visual representations based on image recognition techniques.In our paper, we describe a visual analysis tool which takes a WUI screenshot and produces structured and machine-readable representation (JSON) of the interface elements' spatial allocation.The implementation is based on OpenCV (image recognition functions), dlib (trained detector for the elements' classification), and Tesseract (label and content text recognition).The JSON representation is used to automatically calculate several metrics related to visual complexity, which is known to have major effect on user experience with UIs.We further describe a WUI measurement platform that allows integration of the currently dispersed sets of metrics from different providers and demonstrate the platform's use with several remote services.We perform statistical analysis of the

In the last few years, many smart objects found in the physical world are interconnected and communicate through the existing internet infrastructure which creates a global network infrastructure called the Internet of Things (IoT). Research has shown a substantial development of solutions for a wide range of devices and IoT platforms over the past 6-7 years. However, each solution provides its own IoT infrastructure, devices, APIs, and data formats leading to interoperability issues. Such interoperability issues are the consequence of many critical issues such as vendor lock-in, impossibility to develop IoT application exposing cross-platform, and/or cross-domain, difficulty in plugging non-interoperable IoT devices into different IoT platforms, and ultimately prevents the emergence of IoT technology at a large-scale. To enable seamless resource sharing between different IoT vendors, efforts by several academia, industry, and standardization bodies have emerged to help IoT interoperability, i.e., the ability for multiple IoT platforms from different vendors to work together. This paper performs a comprehensive survey on the state-of-the-art solutions for facilitating interoperability between different IoT platforms. Also, the key challenges in this topic is presented.

Each day, a vast amount of data is published on the web. In addition, the rate at which content is being published is growing, which has the potential to overwhelm users, particularly those who are technically unskilled. Furthermore, users from various domains of expertise face challenges when trying to retrieve the data they require. They may rely on IT experts, but these experts have limited knowledge of individual domains, making data extraction a time-consuming and error-prone task. It would be beneficial if domain experts were able to retrieve needed data and create relatively complex queries on top of web documents. The existing query solutions either are limited to a specific domain or require beginning with a predefined knowledge base or sample ontologies. To address these limitations, we propose a goal-oriented platform that enables users to easily extract data from web documents. This platform enables users to express their goals in natural language, after which the platform elicits the corresponding result type using the algorithm proposed. The platform also applies the concept of ontology to semantically improve search results. To retrieve the most relevant results from web documents, the segments of a user's query are mapped to the entities of the ontology. Two types of ontologies are used: goal ontologies and domain-specific ones, which comprise domain concepts and the relationships among them. In addition, the platform helps domain experts to generate the domain ontologies that will be used to extract data from web documents. Placing ontologies at the center of the approach integrates a level of semantics into the platform, resulting in more-precise output. The main contributions of this research are that it provides a goal-oriented platform for extracting data from web documents and integrates ontology-based development into web-document searches.

The number of web documents as well as the inherent data and information is growing at a rapid pace. The interest in extracting and utilizing this data is rising likewise. The prospects that are unlocked by Web Data Extraction to its users are as broad as the extensiveness of topics and fields on the Web. The major obstacle is to utilize the available data, contents and processes. Several, mostly older survey papers have already shown developments and approaches to solve Web Data Extraction tasks, but there is a need for a more up-to-date review, showing the latest developments. Additionally when looking from the user perspective, there is still a gap between research results and practical applicability. Available solutions, including research results, commercial products and open source solutions lack certain capabilities or suffer from severe usability issues. This paper therefore gives a short review of the state of the art in Web Data Extraction and relates this to the practical application of these technologies.

Over the past 20 years, search engines have become emph{the} entry point of the WWW. Due to evolving needs for different and new kinds of information, the interfaces of search engine results pages (SERPs) change over time. Thus, their usability must be continuously evaluated to ensure user satisfaction and competitive edge. As no complete solution exists, we present emph{S.O.S.:} the emph{SERP Optimization Suite}. Our approach comprises (a) emph{WaPPU}, which is a near real-time tool for evaluating web interfaces based on usability scores, and (b) a emph{catalog of best practices} that maps bad scores to potential causes and corresponding adjustments for optimization. During a case study in which we assessed and optimized a real-world SERP, S.O.S. has proven its feasibility and effectiveness by significantly improving the SERP's usability.

Web application development lacks simple reuse of client-side components. In the last years, many component-like parts of web applications were provided as JavaScript libraries. However, those are mostly not self-contained, require cumbersome configuration and instantiation and can cause conflicts with existing elements. Furthermore, developers need advanced knowledge of JavaScript and the composition of multiple components is difficult. In this paper, we propose the usage of enhanced web components to bring component-based software engineering to the Web. Based on the latest developments of the family of W3C standards called "Web Components", we present our SmartComponents, which are a part of our SmartComposition approach. We provide loosely coupling and support both single- and multi-device usage by extending standard Web Components with dedicated communication and synchronization features. SmartComponents are independent, encapsulated, configurable and programmable. We demonstrate our SmartComposition approach by presenting an exemplary application using various SmartComponents to showcase web application development through client-side composition.

With increasing complexity of web-based applications, traditional engineering from scratch becomes an effortful matter with security aspects difficult to oversee. By composing applications from reusable building blocks, component-based web engineering approaches promise to reduce time to market while providing flexibility to changing conditions. Yet, they face a trade off between developing software in an agile fashion and establishing a solid security foundation.

It is crucial for the success of a search-driven web application to answer users' queries in the best possible way. A common approach is to use click models for guessing the relevance of search results. However, these models are imprecise and waive valuable information one can gain from non-click user interactions. We introduce TellMyRelevance!---a novel automatic end-to-end pipeline for tracking cursor interactions at the client, analyzing these and learning according relevance models. Yet, the models depend on the layout of the search results page involved, which makes them difficult to evaluate and compare. Thus, we use a Random Mouse Cursor as an extension to our pipeline for generating layout-dependent baselines. Based on these, we can perform evaluations of real-world relevance models. A large-scale interaction log analysis showed that we can learn relevance models whose predictions compare favorably to predictions of an existing state-of-the-art click model.

WebID is a new development of the W3C. As a universal identification mechanism, WebID enables users to authenticate through client certificates instead of username/password pairs. For creating such WebID certificates, there are different ways available. Each is characterized by several aspects that become important depending on a user's individual conditions and trust needs. Users must carefully consider these aspects on their own to find the most appropriate way for them. There is a risk that inexperienced users make wrong considerations, which affect their security and privacy. In this work, we propose an approach towards a context-aware WebID certificate creation taking individual conditions and trust needs into account. As a proof of concept, we apply the SWAC framework that facilitates JavaScript-based generation of WebID certificates on both client and server. We evaluate our approach and available methods including HTML5 keygen and native implementations using different devices and Web browsers.

Web application frameworks are a proven means to accelerate the development of interactive web applications. However, implementing collaborative real-time applications like Google Docs requires specific concurrency control services (i.e. document synchronization and conflict resolution) that are not included in prevalent general-purpose frameworks like jQuery or Knockout. Hence, developers have to get familiar with specific collaboration frameworks (e.g. ShareJS) which substantially increases the development effort. To ease the development of collaborative web applications, we propose a set of source code annotations representing a lightweight mechanism to introduce concurrency control services into mature web frameworks. Those annotations are interpreted at runtime by a dedicated collaboration engine to sync documents and resolve conflicts. We enhanced the general-purpose framework Knockout with a collaboration engine and conducted a developer study comparing our approach to a traditional concurrency control library. The evaluation results show that the effort to incorporate collaboration capabilities into a web application can be reduced by up to 40 percent using the annotation-based solution.

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.

Today's Web applications and their respective business processes reside under the control of different organizations. Establishing federations between these organizations, i.e. bringing these business processes together by transcending organizational and security borders, raises a new class of security questions concerning the management of trust relationships between the autonomous bodies that wish to work together. Based on the Webcomposition architecture model we provide a modeling approach for federated Web applications. In this paper we present a methodology for formalizing these models using the ambient calculus for use in further computation. Based on the results we help the users to identify and detect security related aspects in Web-based federations.

Modern software solutions for distributed applications show a strong need for fast and flexible integration of heterogeneous service technologies, as well as for the orchestration of traditional service-based business scenarios (e.g. SOAP or RPC) and REST-driven approaches. The fulfilment of these requirements in existing enterprise platforms is typically accomplished with parallel working components based on different technologies and APIs, resulting in architectural overhead and increased complexity. The WebComposition/DGS (Data Grid Service) aims at solving this issue with the help of a central service layer which specifies a common plug-in framework used to adapt concrete service protocols and which offers an easy-to-use interface for deploying new logic and services. This approach reduces development effort and overall costs thanks to its coherent and integrated DGS-compatible service architecture with automated support for several protocols.

Comparing context of different entities is not easy at all. Since context depends on the situation of a particular entity it can be understood in different ways by various entities. In this paper we introduce an approach to consider all entities as environment in which the formal interpretation of all available context and its changes can be quantified and used to find optimal decisions within such an environment-aware system.

Complex dialogs with comprehensive underlying data models are gaining increasing importance in today's Web applications. This in turn accelerates the need for highly dynamic dialogs offering guidance to the users and thus reducing cognitive overload. Beyond that, requirements from the fields of aesthetics, Web accessibility, platform-independence, and Web service integration arise. To this end, we present an evolutionary, extensible approach for the model-driven construction of advanced dialogs. It is based on a Domain-specific Language (DSL) focusing on simplicity and fostering collaboration with stakeholders.

The success of many innovative Web applications is not based on the content they produce -- but on how they combine and link existing content. Older Web Engineering methods lack flexibility in a sense that they rely strongly on a-priori knowledge of existing content structures and do not take into account initially unknown content sources. We propose the adoption of principles that are also found in Component-based Software Engineering, to assemble highly extensible solutions from reusable artifacts. The main contribution of our work is a support system, consisting of a central service that manages n:m relationships between arbitrary Web resources, and of Web application components that realize navigation, presentation, and interaction for the linked content.

Electronic devices have been used for the support of everyday tasks in domestic and professional environments for some time now. Currently, there is a tendency towards a combined application of individual gadgets that are connected within locally confined environments via a diversity of protocols and technologies like UPnP, WLAN and Bluetooth. As one step further in this direction, there is the vision of devices that are globally and uniformly connected through the WWW, extending the Mobile Web to a Ubiquitous Web. Hence, this allows for scenarios where actions on one device can trigger events on an arbitrary other device, and where third-party Web services from anywhere in the world are involved. Ultimately, this results in federations of devices and Web services belonging to different households, companies, suppliers and service providers, forming new kinds of Web applications that integrate devices as an additional dimension. To fulfill this vision, solutions are required that are able to abstract from the different device implementations and bridge the gap between the device and the Web. In this paper, we present the Federated Device Assembly (FDX) approach that offers an integrated management platform for wrapping and as such connecting arbitrary devices to enable new forms of Web applications along with the means to model such federations. Furthermore, we demonstrate how the required infrastructure systems can be realized by introducing a reference architecture and a generic Web service interface.

Establishing efficient and intensive stakeholder collaboration is a key factor in Web application development projects. Therefore, the form of collaboration needs to be shifted from simple conversation to valuable contribution, i.e. empowering stakeholders to directly contribute to the development effort. To achieve this, we introduce an approach combining Domain-specific Languages and an underlying technical platform.

Today, the Web is increasingly used as a platform for distributed services, which transcend organizational boundaries to form federated applications. Consequently, there is a growing interest in the architectural aspect of Web-based systems, i.e. the composition of the overall solution into individual Web applications and Web services from different parties. The design and evolution of federated systems calls for models that give an overview of the structural as well as trust-specific composition and reflect the technical details of the various accesses. We introduce the WebComposition Architecture Model (WAM) as an overall modeling approach tailored to aspects of highly distributed systems with federation as an integral factor.

Strong user involvement and clear business objectives, both relying on efficient communication between the developers and the business, are key factors for a project's success. Domain-Specific Languages (DSLs) being simple, highly-focused and tailored to a clear problem domain are a promising alternative to heavy-weight modeling approaches in the field of Web Engineering. Thus, they enable stakeholders to validate, modify and even develop parts of a distributed Web-based solution.

The rapid advance of technologies like Web services enables solutions to exploit more and more of the potential of the Web in many ways, recently especially in the field of federating distributed systems within or between businesses. To sustain maintainability and cope with the evolving application life cycles, a global uniform view on all involved sub systems and underlying infrastructure is required. This can be provided by a model that serves as a map for the landscape of the overall system to act as a guide to evolution. In this paper, we introduce the i2Map as an approach to these modeling demands focused on federable Web-service-based applications.

Managing a highly connected and heterogeneous computing environment requires the federation of various management systems (managers) across different platforms, technologies and systems. This research work is focusing on a generic manager-to-manager (M2M) interface, which enables a seamless cooperation between autonomous managers on the basis of Web services. Next to the standard Web services protocol stack, further emerging Web services specifications are reviewed in depth for the usability in this case study.