328 Personal Content Experience: Managing Digital Life in the Mobile Age over 4 million sites and over 590 000 categories as of August 2006). The same signifi cant growth has taken place in other user-contributed 2 projects, such as freedb, and may become an important factor in defi ning universal ontologies. • Open ontologies needed for scale-up What is essential in this respect is the interoperability between dif- ferent ontologies. This is a huge challenge, and it is likely that the ontologies will remain incompatible for several years to come, primar- ily due to their anarchistic nature of evolution and the inherent diffi - culty of knowledge representation. SHOOT THE BASS PLAYER Eddie took Angie to see The Kinkees’ gig in The Hard Rat Hall. She’s not really into their retro-punk music but, having listened through Eddie’s playlists dozens of times, she knows most of the songs. The gig is great, the band seem to be really wound up, the audience is packed and jumping up and down. As usual everybody is fi lming and bootlegging the band, as they explicitly invite con- tributions to enhance their OuterSpace site. The bassist is quite cool, Angie thinks. He’s not your dad’s bass player who would stand quietly in the corner. No, this guy is up there, fl ying those silly rock jumps in sync with the lead guitarist. Kind of cute, too. Who is that guy? Why does he look so familiar? Angie works her way to the side of the stage. The speakers are pumping air so that her blonde hair is fl own in her face. Loud, but fun. She gets just next to the bassist, he sees her waving and poses for her in that rockstar fashion while she snaps an image. Wow, I’m a real fan now, Angie muses. Angie uploads the image to RokkenRoll, the prominent rock music trivia archive. Angie sees that the site features live footage from tonight’s show. Looks like a number of people there were uploading too. Angie queries the service for match- ing images of the bass player. It turns out there are hundreds of matches – this guy must be famous – so she limits the search by the context information of the event that other people have already fed in. That’s better, about 15 matches. One of the images has already been tagged with the bassist’s id: Roy Kee. Weird name. The id is a live link, which Angie saves for later perusal. She could also chat with other audience members and locally share footage of the gig, but not now, thanks. Now it’s time to fi nd her way back to Eddie, who’s somewhere there in the middle of that cheering and waving crowd. She jumps in to dance. This music actually rocks after all . . . 2 http://www.freedb.org/