Abstract. The Keystroke-Level Model (KLM) is a model for predicting the execution time of routine tasks. Initially, it had been devised for standard keyboard-desktop settings but an extension of this model for interactions with mobile phones has been described by Holleis et al. [10]. We propose a considerable update of this KLM focusing on NFC-based applications and interactions which are continuously gaining interest. Insufficiencies within the previous model regarding operators for Pointing, Mental Acts, and System Response Time are treated. We present the results of several studies conducted in order to update the values of these operators. A specific focus is put on the differences between static (NFC tags behind a printed poster or object) and dynamic interfaces (tagged displays or projections). Finally, we validate our results by modeling two applications with the former and the proposed model. The latter performed consistently better when compared with measurements from real user interaction data.

Abstract-Mobile interactions with public displays are often indirect and not very convenient for multiple users at the same time. In this paper we use the physical, touch-based interaction with Near Field Communication (NFC) to investigate direct mobile interactions with public displays for multiple users. For that purpose, we adopt the Whack-a-Mole game for dynamic NFC-displays, which combine the physical interaction with NFCtagged objects and the visual output capabilities of public displays. We show that a grid of NFC-tags can be used to implement direct mobile interaction with public displays in general and a highly interactive multiplayer game in particular. Our study shows that users appreciate this physical, NFC-based mobile interaction, although technical advances are still necessary in order to improve its recognition rate of about 70%. The study also indicates that users are willing to interact with large displays in public, but prefer private or semi-public places, where their interactions attract less attention.

No abstract

No abstract

No abstract