viii Personal Content Experience: Managing Digital Life in the Mobile Age 4.7 The PCE Trinity: Mobility, Context and Metadata ...................................................... 111 4.7.1 File Context ......................................................... 112 4.7.2 Elements of Context ............................................. 114 4.7.3 Context is Essential for Communication ............... 115 4.8 The Challenges: Universal Metadata, Extensibility, Abuse ............................................. 116 4.9 Yet Another Challenge: Interoperability ............. 118 4.9.1 Personal Content Device Ecosystem ..................... 118 4.9.2 Application Interoperability .................................. 120 4.9.3 Existing Solutions for Interoperability .................... 120 4.10 The Dream: When Metadata Really Works ................................................................ 122 4.11 References ......................................................... 124 Chapter 5: Realizing a Metadata Framework ................. 127 5.1 Metadata is a Solution . . . and a Problem ............................................................... 128 5.2 Challenges in Distributed Mobile Content Management ....................................................... 130 5.2.1 Storage ................................................................. 130 5.2.2 Synchronization ................................................... 133 5.2.3 Version Control .................................................... 134 5.2.4 Backing Up .......................................................... 135 5.2.5 Content Adaptation .............................................. 136 5.2.6 Locating the Desired Piece of Content ................. 138 5.3 Different Types of Metadata ............................... 140 5.3.1 Tags ..................................................................... 141 5.3.2 Context Capture .................................................. 142 5.3.3 Relationships ........................................................ 145 5.3.4 Usage History and Events ..................................... 147