Designing for the Internet of Things

What is interusability?

Charles Denis and Laurent Karsenty first coined the term ‘inter-usability’ in
2004 to describe UX across multiple devices^1. Conventional usability theory is
under-equipped to cope with cross-platform design. However, one 2010 paper
by Minna Wäljas, Katarina Segerståhl, Kaisa Väänänen-Vainio-Mattila and
Harri Oinas-Kukkonen proposes a practical model of interusability^2.

Wäljas et al propose that the ultimate goal of cross-platform design is that the
experience should feel coherent. Does the service feel like the devices are
working in concert, or does the UX feel fragmented?

They define three key concepts for cross-platform service UX, which together
ensure a coherent experience:

P Composition: how devices and functionality are organized

P Appropriate consistency of interfaces across different devices

P Continuity of content and data to ensure smooth transitions between

platforms

The paper was published in 2010 and the services evaluated (including Nike+
and Nokia Sportstracker) now inevitably feel a little dated. But we have found
the model still holds up well in our own work designing IoT services, and it’s
a key reference for the rest of this chapter.

(^1) Denis, C. and Karsenty, L. (2005) Inter-Usability of Multi-Device Systems – A
Conceptual Framework, in Multiple User Interfaces: Cross-Platform Applications and
Context-Aware Interfaces (eds A. Seffah and H. Javahery), John Wiley & Sons, Ltd,
Chichester, UK
(^2) Wäljas, M., Segerståhl, K., Väänänen-Vainio-Mattila, K., Oinas-Kukkonen, H.:
Cross-platform service user experience: a field study and an initial framework. In:
Proceedings of the 12th International Conference on Human Computer Interaction with
Mobile Devices and Services, MobileHCI 2010, p. 219. ACM, New York (2010). I’ll
refer to this paper several times in the rest of this chapter as Wäljas et al, although I
understand that Katarina Segerståhl was the primary researcher. Her PhD, available at
http://herkules.oulu.fi/isbn9789514297274/isbn9789514297274.pdf, builds on the same
concepts.