OWCG

User interfaces (UI) are a central part of every application. They must ensure appropriated usability and information presentation in order to let users control
the application. When concerning wearable user interfaces (WUI), this becomes even more challenging. Limitations of special I/O devices used for interaction or presentation in wearable computing (e.g. HMD's or data gloves) strongly vary
from devices used in stationary or mobile computing, where WIMP (Windows
Icons Menus Pointing) interfaces dominate.

Currently, WUIs usually have to be designed from scratch without common standards regarding there appearance or control being established. Such
individually designed interfaces, however, have the drawback that they are
not easily reusable in other configurations. Thus, they can not be used to
reduce implementation efforts for WUIs nor can users get familiar with using wearable computers.

Due to the fact that successful software applications always come along with successful user interfaces and interaction concepts for the application domain, different objectives have to be tackled in order to make wearable applications successful. The following standardization objectives have been identified to
support wearable computing in the field of user interfaces and interaction
design:

- Abstract UI Description Language: even in the beginning of newly emerging wearable computing hardware, application developers will be faced with the problem of lacking knowledge of how to design wearable applications, as they are currently only used to develop desktop or mobile applications. With the availability of abstract UI description languages developers no longer have to design the user interface while programming it, but could describe it in an abstract manner. Since today developers are familiar with using XML based languages description languages (e.g. HTML, WSDL, etc.), the description language should also be using that standard. There are already different standards available that target the abstract description of an UI, however, often developed for desktop applications. Therefore, extensions to such standards making them better suited for wearable computing should be pursued.

- Device Description Standards: regardless whether WUIs will be implemented or described with appropriate languages, one critical aspect of the interface has still to be managed: the interaction. Unlike in stationary computing were developers can assume a standard computer setup consisting of a display, standard PC hardware, keyboard, and a mouse device, wearable computing application developers cannot. As wearable computers will typically be used “mis­sion specific”, rather than general purpose, there will not be the necessity for a set of standard I/O components existing in every wearable computer. Therefore, device description languages (DDL) are required, that on the one hand can describe the capabilities of wearable I/O devices sufficiently and on the other hand can be used by a standardized “device lookup” system running on every wearable computer to allow applications to access available devices.

- Multi-modal interaction: as mentioned wearable computing gives new opportunities to the way interaction can be designed for an application. However, these new possibilities can make interaction design very complex. Wearable computers and their applications should be designed by definition as unobtrusive and as closely integrated in the work process as possible. The best way to achieve this regarding interaction design is obviously by designing the human-computer interaction as close as possible to natural human-human communication, i.e. enabling interaction with a combination of different modalities, e.g. pointing and speaking, at the same time to control an application. The Extensible Multimodal Annotation Mark-up Language (EMMA), developed as a data exchange format for the interface between input processors and interaction management systems, could possibly be used for implementing such capabilities into applications.

- WUI Design Guidelines and Interaction standards: if wearable computers will become more and more widespread the amount of available applications will increase. To assure ergonomics of applications including aspects, for example, like consistency over different applications that it needed to allow users to become familiar with the new computing paradigm, WUI style guides are required. Those style guides might be comparable with existing ones for the different desktop operating systems (Macintosh, Unix, Windows, Symbian OS) or interaction paradigms such as WIMP (Windows, Icons, Menu, and Pointing). As wearable computing is very different from other existing computing paradigms (such as stationary computing or mobile computing) existing guides are not applicable but could possibly be used as a template.