54 Personal Content Experience: Managing Digital Life in the Mobile Age Personal content is content that the user has a voluntary relationship 6 with, and is in possession of or has control over. Now, with this characterization, we can start discussing personal content in detail. 3.2 Categorization In order to understand the nature of personal content, one needs to understand more of its inherent features. What is it like? How does it behave? What are the mechanisms used to manipulate it? How do personal content items relate to each other? How do they relate to external entities? A common way of describing a phenomenon is to fi rst categorize it. Categorization is a strong tool for understanding and managing any complex phenomenon. An obvious, intuitive categorization criterion is by content modality. Basically all current human-accessible digital content types can be clas- sifi ed into three main categories: the content is primarily visual, audi- tory, or tactile. In the future, we may also have olfactory and gustatory content. However, the above classifi cation is superfl uous, as it does not clarify the characteristics of personal content. For instance, how should one classify saved games? Saved games provide parameters for recreat- ing a particular context of a virtual world, complete with the environ- ment, characters, and objects (section 7.4). It is meant entirely for human access, but not to any particular senses. Mostly, it results in a visual presentation of the world; additionally, it may also contain audi- tory elements. Above all, though, it contains information that enables us to experience the virtual world with our senses and imagination. Another way to classify personal content types is by their internal representation, that is, the way the bits are to be interpreted: • text: SMS, e-mail, e-books, chat session logs; • images: photos, drawings, scanned paintings; • audio: music, ring tones, earcons; • video: movies, clips. With this kind of classifi cation, however, we will quickly run out of higher-level terms; for any content type arranged differently from the 6 And then again, when your partner asks you to take yet another photo of yet another fabulous sunset, the voluntary nature of the content experience is to be doubted.