Integrated Accessibility Models of User Interfaces for IT and Automation Systems Peter Göhner, Simon Kunz University of Stuttgart IAS {peter.goehner,simon.kunz} @ias.uni-stuttgart.de
Sabina Jeschke, Helmut Vieritz University of Stuttgart RUS & IITS {sabina.jeschke,hemut.vieritz} @rus.uni-stuttgart.de
Abstract The difference between user interfaces of computer and Web applications on one hand and the interfaces of actual machines and devices is becoming smaller. By this the importance of comprehensive – meaning the inclusion of both types of systems – accessibility and usability concepts is getting bigger. The aim of this research project is to provide functionality even under difficult circumstances. Among these we have individual difficulties of a user (disabilities) and environmental disturbances (noise, bright light) as well as constraints that are arising from the technology that the user has at disposal. This project’s emphasis is on two points: To unify accessible user interfaces for computers, machines and devices and to simplify the development of such by a model-based development approach. With the help of a user-centered approach, we will first specify the different demands on user-interfaces. After that the demands will be integrated into the modeldriven development approach of the Model-Driven Architecture (MDA). Due to the universal approach, it is possible to do justice to the increasing fusion of user interfaces of Web and desktop applications with the ones of automation systems. 1
INTRODUCTION
Accessibility of information can be limited by several aspects. Amongst these are demands: • by special user interfaces e.g. mobile devices with small screens or no audio output, • by users with certain restrictions of perception, motor activity, or mental processing of information and • arising from the user’s environment; e.g. bright light, loud noise, unwanted audio output and more. These aspects can be divided into user-, platform-, or environment-specific demands. They are not only pertaining to disabled users. Two scenarios will make this clear. • Scenario Workstation for a Blind Person A blind user at an IT-workstation uses Web-based services of the employer. She is using a computer with refreshable Braille display and a screen reader-software as well as a keyboard. To assist communication with her colleagues she can also use a normal screen. Problems are arising from web pages with confusing design or from information represented by pictures without the possibility of an alternative representation. Email and instant messaging help to exchange information between colleagues and whenever some information cannot be found via the intra-
Olivier Pfeiffer Technische Universität Berlin MuLF
[email protected]
net, our user is using these means for asking colleagues. • Scenario Maintenance of Automation Systems – Environmental Constraints and Manual Activity In this scenario the workflow of a maintenance procedure for an automation device will be examined in detail. For error-diagnosis the maintenance technician uses a diagnosis-notebook to access the automation device. In parallel, manual measurements have to be made at the device directly. Because the same senses have to be used for different purposes, this slows down the entire procedure and requires frequent rethinking by the technician. This increases workload [1] as well as it makes the process more susceptible to errors. Where big devices need maintenance the environmental conditions have to be taken into account as well. If at a part of the device that’s difficult to access a securing by hand is necessary, the technician cannot use them to operate haptic input devices. Despite the fact that both scenarios describe quite different situations comparable restrictions can be found within the use of mono-modal user interfaces. The general idea to solve this problem is to multimodally present all information by the application and the UI. In interpersonal communication also combinations of different modalities of the senses are being used. Often we combine spoken words with facial expressions and gestures. Persons with sensorical constraints can have other senses more pronounced like the sense of smell or of touch. By using different interaction-channels of the user for the humanmachine-interaction a greater flexibility of the interface with regard to the adaptivity to environmental constraints or in general to restricted possibilities of interaction of the user can be provided. For the purpose of designing technical systems more intuitive and therefore keeping the increasing complexity controllable by the user, studies about the future developments of automation technology are recommending the use of multi-modal human machine interaction [2]. Compared to the human organism, technical systems either provide significantly less communication channels or these channels are severely limited in their capability [3]. In general, out of all possible modalities of the senses, especially the tactile, the visual and the aural channel are of importance for technical applications [4]. The use of any of the other channels is only relevant for single selected special applications and can be neglected for real-world solutions in technical systems. 1.1
Accessibility The development of accessible desktop- or Web-based
applications is still a complex process. Until today these applications are outnumbered although guidelines and recommendations exist since some considerable time. Computer-based applications can adapt their presentation of information to the particular needs of each user and offer new approaches for distributing and communicating information. But still general approaches realizing this are missing. Accessibility is the quality of the user interface (UI). However, it influences the structure and functionality of the application like the underlying data model. Experts accentuate that accessibility requires less extra effort when respected from the beginning of the design process. Hence, it is necessary to start the conception with the design of the UI. This so-called user-oriented approach integrates structure and functionality of the application into the requirements of the UI. The ability to flexibly present information and knowledge according to the requirements of the individual user is an advantage of desktop applications and dynamic web platforms regarding barrier free services. Here the separation of layout and content und the basic idea of the semantic web is the main point. This means however, that every relevant information concerning content, navigation, presentation, etc. has to be available in a semantic description. This is the condition for web applications to be able to include and present this information in an appropriate way. At present the most common guidelines for accessibility of digital information are the recommendations of the W3C for the layout of barrier free information services [5]. As they mainly focus on presentations for the internet they are fitted to the context of static services in the WWW. The requirements of interactive, dynamic and multi media web applications like modern knowledge management platforms are not covered by this recommendation and the requirements of visual interfaces of industrial automation applications are not regarded at all. The most important innovations of version 2.0 [6] of these guidelines are the independency of a certain web technology and a better ability for validation. Thus the new guidelines are the adequate origin for the definition of own requirements for accessible user interfaces. The high degree of popularity, the focus on the IT technology and the independency of special technological standards have been the reasons to choose these guidelines out of many existing guidelines focusing different operational areas [7]. The chosen guidelines do also perfectly fit for abstract approaches and for the integration of model driven development approaches. Although model driven software development is established within industry, its potential for the development of accessible applications is hardly discussed. Publications targeting this topic – i.e. the Dante project [10] and the BeLearning project [11] – are rare. 1.2
Automation Systems In industrial automation, a trend to implement more
and more functionality in software can be observed. The augmentation of the existing functionality is thus less and less limited by the given hardware. So the simple implementation of new functionality is possible which leads to more complex systems. Furthermore the pure functionality is less and less useful as classification criteria for distinction between competitors [12]. Thus the humansystem-interface plays a more and more important role for purchase decisions. This tendency can be observed at consumer marked of automation products. Facing the functional range of today’s mobile phones, the functionality of mobile phoning is only of subsidiary interest, while the usability considering different abilities and preferences of the user (e.g. old users) gets more and more important. Research is addressing the question, how the increasing complexity of technical systems can be transformed in such a way, that humans are still able use them. Intuitive concepts that consider the usage of multiple human senses as well as developments regarding the “Joy of Use” [13] have to be named here. This is one topic that is more and more focused within new product developments. A systematic integration of these approaches in the model driven development process for human machine interfaces has not been performed yet. 1.3
User-Centered Method
A procedure for the development of user interfaces that emphasize the ability, tasks and needs of the user, is described in DIN EN ISO 13407 [14]. The norm is defining an iterative process of user oriented layout activities. At the end of each iteration step, the generated layout solutions, the requirements of the user and the focused user context are balanced. If required the requirements are specified more precisely and improved in the subsequent iteration step. In current research thesis [15] tool concepts are developed, which implement these requirements of the user driven development and which thus are able to support the development process. The accessibility of the user interface as well as the interaction with different human senses are not addressed in these theses, no more differences between the information processing of different people. The approach presented here is using up-to-date research results of the fields presented to reach two goals within the conception of accessible user interfaces by means of a model-driven development method, namely: • Simplifying, this will help architects and developers of software with their work and makes additional special knowledge of accessibility – at least partially – unnecessary. • Unifying for different fields of application. • Simplifying, that software architects and software developers are supported and are – partly – released from the must of having knowledge of accessibility • Unifying for different application domains.
2
RELATED WORK
Technically motivated methods of user interface development like User Interface Design Language (UIDL) [16] or User Interface Markup Language (UIML) [17] map real implementations of user interfaces into an abstract model. They do not support early analysis or the planning of interfaces. Useware Markup Language (useML) [18] is an XML-conform markup language for useware engineering. It is based on user task modeling and supports early analysis in the pre-modeling phase. Structure modeling is supported but the modeling of details and layout of the resulting UIs is not. The development process is characterized by a possible early evaluation of interface prototypes. User Interface Extensible Markup Language (UsiXML) [19] is another XMLconform markup language for UIs in multiple contexts. It aims to include diversified types of UIs for desktop- or Web-based applications. The resulting types of models are more abstract than the ones resulting from other approaches. UsiXML supports the entire modeling process from the beginning on. Early analysis is not supported. The Dante project [12] aims at improving the access for visually impaired people to Hypermedia environments – especially the Web. It is focused on devising a tool to analyze and transform Web pages using a model-driven approach and generating annotations from the design specifications. Usually, visually impaired users have to rely on screen readers. This assistive technology reads the content sequentially and cannot detect and present the meaning of different page objects. Without further information this implicit knowledge of the structure is not accessible to visually impaired people. Extra semantic annotation can avoid the problem if the screen reader is provided with additional semantic information. The Dante-approach allows semantic annotation of Web pages to explicitly provide knowledge about structure and to support screen readers to facilitate the audio presentation of the content. The identified objects are annotated with terms from the Web Authoring for Accessibility ontology (WAfA). Currently, such annotations are done manually and do not address the problem of dynamic content. In combination with the user-centered Web Site Design Method (WSDM) [19] it is possible to fully automate the generation of semantical annotations used for Dante [20]. It is estimated that 85% of the annotations can be provided this way, making Dante very interesting for dynamically generated content. 3.
APPROACH
We have the following demands on the approach presented here: Simplicity: Modeling has to be simple enough. The integration of the accessibility requirements should not bring a complexity of modeling that is too high. Support of analysis: The approach should be helpful already in analyzing the demands, so that architects
resp. developers will be supported early in obeying the requirements. Support of standards: The support of existing standards (resp. standardization efforts) helps to increase the attractivity of the approach and lessens the effort of becoming familiar with the approach. Starting point of the approach presented is a useroriented model of proceeding [12] for the development of machine-interfaces. Features of the useML-approach are a support of the analyzing phase as well as simplicity. Whereas the downside is currently apart from supporting the basic structure of the user interface, no support of modeling is present. Therefore enhancing the approach is necessary to support • modeling of the application-logic. • generating the abstract and concrete models of the user-interface. • more complex layouts with multimedia elements like graphics, videos, sounds etc. Modeling starts with the analysis of workflow processes which the application shall support. Thus, it bridges the gap to technically motivated methods. Pre-modeling activities like Systematic Layout Planning (SLP) serve to identify the details of work flow and to analyze the mental models of to-be users. Especially mental models of users handicapped by birth significantly differ since the kind of imagination depends on the modality of perception during early socialization.
1. The models at a glance The goal of the process is a detailed allover-model of the accessible user interface including the description of the communication between the interface and the other tiers of the application. The process is focused on Web applications and Graphical User Interfaces (GUIs). The models are coded in XML-compliant languages to provide an accessible modeling process too. UML-based presentation is not accessible for visually impaired people. However, UML-diagrams can be used for modeling. Additionally, XML modeling facilitates the generation of prototypes from models for different platforms using XSLT or XSL-FO. This enables an early evaluation of the models. The evaluation accompanies the modeling and develop-
ment process allover the time to detect open issues at an early stage. The process is structured according to the Cameleon reference framework [21] and the included four basic levels of abstraction Task & Concepts, Abstract User Interface (AUI), Concrete User Interface (CUI) and Final User Interface (FUI). Figure 1 shows the different models in an overview. Modeling starts with a description of tasks to be carried out by a user as use objects in the Task Model and afterwards in detail with the Use Model. Tasks are independent from personal, contextual or technical restrictions. The Use Model extends the XML-description of the Task Model with additional nodes and attributes. The Use Model describes the workflow independent from technology like input and output devices, platform and system. The tasks are separated into activities which can be considered as being atomic. On the other side they are still independent from physical operations to avoid dependency from the used technologies like mouse, keyboard or screen reader etc. These activities can be separated in five classes described in the model as elementary use objects: Inform: query information from the application as text, images etc. Activate: direct triggering of an application function Select: select one or more values from a set with a possible triggering Input: entering new data, maybe text, images etc. Change: modifying existing data with the UI, changing values Some sub-classifications are possible to facilitate further modeling: start/go, stop/exit, create, delete, duplicate, toggle, monitor etc. Part of future work is evaluation and integration of more fine granular techniques like the ConcurTaskTree [22]. The visibility of tasks can be mapped with the help of an additional User Model. Especially complex Web applications require the modeling of users and the declaration of possible user actions and usable functionalities. A hierarchical User Model facilitates modeling whereas independent user groups are easier to use for analysis. In the examples presented here the User Model is not used. The dependencies between activities are included in the Use Model. They already describe a part of the structure of the interface. In the next step, the Use Model is extended with the complete structure of the to-be UI. Elementary use objects are mapped on abstract interaction objects. The derived Abstract User Interface Model describes functionality and purpose of all interaction objects and their relations. The Navigation Model can be derived from the AUI Model and serves for a better overview of the UI structure. Additionally, it can be used to declare the details of the structure. Within the here presented project the roles, states and properties for accessible Rich Internet Applications from the WAI-ARIA are integrated in the specifications of the UI models. This assures that all related information is semantically encoded and can be – at least semiautomatically – transformed into accessible UIs. Of
course, accessibility of hand-written code is not supported. External tools are necessary to facilitate this part of development and part of further research. In the next step of the modeling process the Concrete User Interface Model will be generated from the AUI Model and the Context Model. The Context Model defines and describes the behavior of the different platforms for the application. In the CUI Model is declared the structure and the design of the interface. Depending from the used platform, abstract interaction objects are mapped on elements of UIs like buttons, navigation elements, lists, tables, images etc. The layout of the interface is still missing and is part of the following implementation. At this stage, semantic annotation for accessibility needs is embedded. The CUI objects include GUI functionality and structural relationship. Within the Final User Interface these aspects are mapped on WAI-ARIA roles. The RDF role taxonomy of the WAI-ARIA supports accessible adaptable XML applications using technologies as XHTML, SVG, CSS, Javascript etc. for Rich Internet Applications. Accessibility means each element of the UI has a full and correct description of semantics and behavior, relationships between elements are known and one element has the correct input focus. Additionally for Web applications: properties, states and relationships are valid and accessible via the Document Object Model (DOM). States and properties are used in the WAI-ARIA to describe accessibly the behavior of UI elements. They must be device independent and settable by the author. Additionally, the Application Interface Model is derived from the AUI Model and defines the communication between the UI and the other components of the application architecture. It serves to support the modeling of functionalities in the application layer. It describes the types of data, the mapping between UI objects and functions of the application. It can serve to derive interface classes of a programming language e.g. Java. 3.1
Model-Driven Development
For a long time model driven (model centered) development approaches (i.e. Rational Unified Process [23] und V-Model [24] are used. There models (UML) of the application depending on the different requirements are created at the beginning of the development process. Since the 1980ies numerous approaches have been developed to advance the methods of software engineering for the conception of web-applications a.k.a. webengineering (i.e. Conallen [25], OOHDM [26], OOWS [27], UWE [28], W2000 [29], WebML [30] und WSDM [19]). Here UML also fits very well as it can be adapted to the special requirements due to its good extensibility. But for all that presentational aspects compared to user aspects and navigation aspects cannot be modeled in UML. Problems with the realization of the ideas mentioned before result from the very heterogenic technologies (i.e. HTML, CSS, JAVA-Script) and the various client plat-
forms, that have to be taken into account facing web based applications. At this it is difficult to consider dynamic generation of content (i.e. by the use of PHP, SQL and ASP) as it is common these days. Furthermore updates of the web application at runtime (maintenance and adaption) can not be handled so far. Model-based approaches of the web engineering do not make up a holistic approach yet but focus on either the organization of the web application (organization driven methods) or the data (data driven methods) or the user (user centered or audience driven methods) [31]. Typically classical software engineering approaches are augmented with three further models: user model, navigation model und presentation model. Whereas integrating the requirements for accessible content has been examined in single cases only. Within the Dante project [12] it has been investigated for example, how annotations can be generated by the use of WSDM, that supply screenreaders with additional information for navigation within an application. 3.2
Integration into the MDA Approach
The goal of the third focus of research is the integration of the requirements of accessible interfaces into the procedures of the MDA. The MDA is in contrast to CASE approaches (computer aided software engineering) not bound to a certain architecture. Thus the MDA is suitable for the various architectures of web applications. Very important for this research project are interaction based architectures or rather architecture patterns [32] as for example the model view controller (MVC) concept or the presentation abstract control (PAC) concept. In comparison with the model driven software development (MDSD) the fixed meta model of the MDA is UML. Thus realization of the results is possible by the use of existing tools. The chosen user centered method takes the requirements of accessible interfaces into account by making the general aspects of accessible user interfaces that are not considered within other approaches, the center of the designs. These aspects can be described independently of the particular application logic and function logic. Former works [33] demonstrate the feasibility of this procedure. MDA does not intend to generate complete code. This is important, as it can be assumed that the implementation of the requirements for barrier free web applications can not be done completely automated. The use of the MDA is suitable for desktop applications as well as client server applications. Thus MDA is a candidate for the integration of the special requirements of accessible user interfaces into the architecture of the application. On one hand MDA is powerful and flexible enough that manual post-work can be integrated, on the other hand MDA offers best perspectives for the integration of the results into the existing research and development scenery by the use of UML. Interoperability is the main goal of the MDA and is at the same time important for the aspired goals of the project. The MDA approach offers an architecture framework
consisting of four architectures that build upon each other and represent the whole architecture together. These architectures are combined with architectonic views, workflows, components, communication and interaction types as well as best practices. The architectures display different abstraction layers: business architecture: (Computation Independent Model CIM): Usecases and concepts describe requirements, processes, etc. in a generally understandable manner. reference architecture: (Platform Independent Model PIM): Components and systems are specified platform independently. Thereto counts interaction and communication of the components. The models are independent of the kind of the component model. application architecture: (Platform Specific Model PSM): Components and systems are described through specific component models, implementation of layer architectures and integration solutions. system architecture: (Enterprise Deployment Model EDM): System specific models describe the implementation of systems and components in a system specific infrastructure. The MDA organizes the development process from the view of the software architects and software developers. Beginning with abstract models the whole architecture is concretized more and more. From the users view it is crucial in the start-up period to define the central functionalities of the system. Simple use case diagrams can be used in this phase to help integrate the customer or the user. Until general requirements of user interfaces can be integrated in this layer it has to be investigated if user functionalities can be described in such an abstract way. The following points play an important role for the modeling of applications [34]: • design of the application • coupling of the application layers • used communication technologies • dependencies from other systems and their interfaces These aspects can be edited by probing of appropriate reference models und reference architectures. This topic is related to the research area of architecture description languages (ADLs). ADLs help to describe software architectures, but industrial experience is missing. As basis elements for applications within technical systems a platform independent usage model is presented in [35]. This model abstracts from the tasks, actions and activities of the user and describes them as usage objects in a model. The basis of the usage model is formed by information, which is extracted within the requirement analysis at the users. Thereby the following criteria are relevant: • static structure of the solution • procedures • required functions and information • execution roles with pre- and post-conditions • priorities and occurrence Basic constructs of the usage models are five elementary usage objects. These objects cover the following subtasks: inform, select, trigger, change and enter. The usage
model is build upon these objects by the use useML [18]. The usage model can be transformed in different output formats afterwards. By the help of this general usage model user tasks and the needed usage functions can be described in a consistent way. The goal of this point of research is the integration of the general usage model in the abstract layers of the MDA, to prepare the conception of accessible user interfaces. References [1] Akyol, S., Libuda, L., Kraiss, K.F.: Multimodale benutzung adaptiver kfzbordsysteme. In Jürgensohn, T., Timpe, K.P.H., eds.: Kraftfahrzeugführung, Berlin, Springer (2001) 137–154 [2] Bretthauer, G.: Automatisierungstechnik – quo vadis? Neun Thesen zur zukünftigen entwicklung. at – Automatisierungstechnik 53(4-5) (2005) 155–157 [3] Althoff, F.: Ein generischer Ansatz zur Integration multimodaler Benutzereingaben. PhD thesis, MMK, Technische Universität München (2004) [4] Althoff, F.: Sounds@Work – Akustische Repräsentationen für die Mensch-Computer Interaktion in kooperativen und hybriden Arbeitsumgebungen. PhD thesis, Technische Universität Darmstadt (2003) [5] World Wide Web Consortium (W3C): Web content accessibility guidelines 1.0. www.w3.org/TR/WCAG10, last access 02/04/2008 [6] World Wide Web Consortium (W3C): Web Content Accessibility Guidelines 2.0 (Working Draft). www.w3.org/WAI/intro/wcag20, last acc.: 02/04/2008 [7] IBM - Human Ability and Accessibility Center: Developer Guidelines. www.ibm.com/able/guidelines, Accessed: 02/04/2008 (2007) [10] Goble, C., Harper, S., Stevens, R., Yesilada, Y.: Dante – Mobility Support for Visually Impaired Web Travellers. dante.man.ac.uk, Accessed: 02/04/2008 [11] Jeschke, S., Pfeiffer, O., Vieritz, H. - BeLearning: Designing Accessible Web Applications, Proc. o.t. 16th Int. Conf. on Software Engineering and Data Engineering, Las Vegas, June 9-11, 2007, ICSA [12] Zühlke, D.: Der intelligente Versager – Das MenschTechnik-Dilemma. Primus Verlag, Darmstadt (2005) [13] Zühlke, D.: Von ctrl-alt-del zu ambient intelligence. In für Mess-und Automatisierungstechnik, V.G., ed.: GMA-Kongress 2005 - Automation als interdisziplinäre Herausforderung, Düsseldorf, VDI Verlag GmbH (2005) 35–42 [14] Deutsches Institut für Normung e. V., D.D.I.: Benutzer-orientierte gestaltung interaktiver Systeme (1999) [15] Bödcher, A., Ehrmann, M.: Usability-test versus usability engineering. atp – Automatisierungstechnische Praxis 47(10) (2005) 51–57 [15] Luyten, K., Coninx, K.: An XML-based runtime user interface description language for mobile computing devices. In: Design, Specification and Verification of Interactive Systems. Johnson, C.(eds.): Proceedings of
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