Contextual Prototyping of User Interfaces Chris Stary University of Linz Department of Business Information Systems, Communications Engineering Freistädterstraße 315, A-4040 Linz, Austria fax: +43 732 2468 7111, tel: +43 732 2468 7102 email: [email protected], URL: http://www.ce.uni-linz.ac.at/research/TADEUS ABSTRACT based approaches for contextual design and prototyping, it Contextual development differs from traditional user inter- turns out that traditional approaches, e.g. [4], support differ- face development in several ways: It focuses on the context ent perspectives on development knowledge, but tend not to of usage and the user population rather than on the techni- model how a system might be used by users in accomplishing cal features required for interaction. However, the latter their work tasks. come into play when transforming context specifications These approaches rather attempt to provide designers into user-interface code. Contextual development also con- with structured facilities for engineering user interface soft- siders design to be a non-linear process based on activities ware, e.g., [11,15]. They lack structured representation of (re)engineering work processes rather than performing context (tasks, users or work processes) as well as mecha- traditional software-engineering tasks. Consequently, con- nisms to transform that knowledge to code. textual development requires usage-relevant (re)pre- Contextual development, however, requires both. Devel- sentation and execution mechanisms. Although the specifi- opments in the field of task-based design, such as ADEPT [8] cation of task- and user-knowledge has been recognized to and MUSE [10], based on experiences with cognitive engi- be crucial for contextual user interface design, seamless neering approaches, such as GOMS [7], enable the represen- development support is still lacking. The reported TA- tation of context information. Their prime concern is to im- DEUS (Task Analysis/Design/End User Systems) project prove design by enhancing its suitability for end user tasks, targets toward an environment that allows contextual and thus implementing the principles of user-centered design seamless design and prototyping based on user and task [12]. Task-based techniques also focus on the process of knowledge. Due to its model-based nature TADEUS is creating design solutions from information about the user's open with respect to diagrammatic notations for specifica- tasks, increasing confidence that the system is compatible tion, and different interaction platforms. As a result, differ- with the tasks it is intended to support. Model-based and task- ent perspectives on the context, development process and based approaches have several features in common [21], such its results can be kept consistent throughout development. as: 1. They both focus on the use of models to represent the Keywords various sorts of information that contribute to the design Contextual design, seamless development, prototyping, of interactive systems. tools, user-centered system design, usability engineering, 2. Both approaches discuss issues pertaining to the use of lifecycle management, object-oriented modeling, interactive the models in design activities (e.g., analysis, evaluation, work design, customization, model-based development generation, verification etc.). Due to their openness model- and task-based approaches are INTRODUCTION candidates to capture the context of user interfaces compre- Contextual development has been recognized to be cru- hensively and derive context-sensitive design solutions. The cial for meeting the demands of user-centred systems design, latter requires a minimal reduction of semantics along the e.g., [16]. Not only particular methods have been proposed, development process, i.e. seamless development, whereas e.g. [2], but also approaches to standardize methodologies, capturing the context requires high expressivity in terms of e.g., ISO DIS 13407. However, seamless development sup- language and tools [11]. port is still lacking. For instance, when considering model- In the following we demonstrate the benefits of combining model-driven and task-based development when reporting on the TADEUS (Task Analysis/Design/End User Systems) Permission to make digital or hard copies of all or part of this work for project. Its seamless methodology and the corresponding personal or classroom use is granted without fee provided that copies development support allow for contextual specification and are not made or distributed for profit or commercial advantage and that prototyping. We detail the steps to be followed throughout copies bear this notice and the full citation on the first page. To copy design based on different perspectives (models), the ontology otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. and diagrammatic (re)pre-sentation scheme for specification, DIS ’00, Brooklyn, New York. and implementation issues. We conclude discussing related Copyright 2000 ACM 1-58113-219-0/00/0008…$5.00. work, achievements, and future research activities. 388 CONTEXTUAL DEVELOPMENT USING TADEUS of work. The user model details the individual perception of The understanding of end users and their organization of tasks, data structures and interaction devices, as well as work requires a conceptual framework of context-sensitive task/role-specific access modalities and permits to data. The components of interactive systems. The TADEUS frame- (problem domain) data model provides the static and dy- work puts the following components into mutual context namic specification of the data-related functionality. It has [19]: task model, user model, (problem domain) data to be derived from the task model. The interaction model model, and interaction (domain) model. For the sake of captures all devices and styles that might be used by the context-sensitivity all of them have to be related mutually, users in the course of interaction. The final specification is statically and dynamically (see also Figure 1). an application model. It integrates and synchronies struc- The task model comprises the decomposition of user ture and behavior specifications. tasks according to the economic and the social organization relate to refine to Task Model Problem Domain Business Data Model Intelligence refine to Model relate to User Model relate to Interaction Domain Model refine to Application Model TADEUS-based user interface development prototype Figure 1: The TADEUS Model-Based Frame of Reference For contextual prototyping, basically three steps have to be mouse buttons). User models become important components performed: of human-computer interfaces, as soon as it is recognized that 1. Task analysis, resulting in a business intelligence model a software system will be able to exhibit user-oriented behav- 2. Task-based design, resulting in an application model ior only if it has access to a user model that holds information (based on the aforementioned models) about users’ characteristics regarding certain tasks being 3. Workflow-driven prototyping, i.e. executing the specifica- performed, as well as the styles and media used for interac- tion of an application model. tion. The analysis of work (step 1) is performed using TATAR (Problem Domain) Data Modeling: Specification of a (TADEUS Task Analysis and Representation technique) [20] semantic data model derived from the tasks and user organi- which leads to a business intelligence model, i.e. a specifica- zation in the problem domain. In contrast to traditional data tion of user and task settings. This model serves as the basis modeling, in TADEUS both aspects of the data required for for the subsequent design activities (step 2) that are described task accomplishment, are captured, namely, the static and the below. dynamic properties. Task modeling: Specification of a task model relevant for Interaction Modeling: Setting up an interaction model is user interface design according to the organization of tasks mostly based on a generic user interface architecture. It and users’ perception of work, usually being a part of the should take into account devices, media, and modalities that business intelligence representation. Task modeling includes are initially considered to be relevant for task accomplish- modeling of the objectives users want or have to meet, ment and user support. A device/widget model is derived probably in response to particular situations or events, as well from the generic architecture. This way, a common look and as modeling of the different activities that users have to per- feel but still platform-conform solution for the application form to accomplish their tasks, as, e.g., given by global and under development can be specified. local business processes. Application Modeling: Final integration of the models, User modeling: Setting up a role model by defining spe- namely the task, user, data and interaction model, through cific views on tasks and data (according to the functional mutually tuning them from a static and dynamic perspective. roles of users), as well as individual user characteristics or This way, the architecture and behavior of the becomes task- particular features for user-adapted interaction, such as re- complete, in the sense that each task that requires interaction quired left-hand assignments to interaction media (e.g., support has been assigned to or has become part of a dialog. 389 The activities described in step 2 do not