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This book constitutes the thoroughly refereed post-conference proceedings of the Fourth International Conference on Mobile Computing, Applications, and Services (MobiCASE 2012) held in Seattle, Washington, USA, in October 2012. The 18 revised full papers presented together with 9 revised poster papers were carefully reviewed and selected from 51 submissions. The conference papers are organized in five topical sections, covering mobile application development, multi-dimensional interactions, system support and architecture, mobile applications, and mobile services.

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Mapping Objective-C API to Java.- A Reference Architecture for Group-Context-Aware Mobile Applications.- Mobile Apps Development: A Framework for Technology Decision Making.- Towards Multimodal 3D Tabletop Interaction Using Sensor Equipped Mobile Devices.- Metric Based Automatic Event Segmentation.- Multilevel and Secure Services in a Fleet of Mobile Phones.- LineKing: Crowdsourced Line Wait-Time Estimation Using Smartphones.- Achieving Targeted Mobile Advertisements While Respecting Privacy.- A Reference Architecture for Mobile Code Offload in Hostile Environments.- Enhancing Traveler Context through Transferable Activity Patterns.

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