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For open-source programmers seeking to compete with commercial software, sync has been a curse as well as a blessing. It is tremendously difficult to design applications that get sync right. The advanced synchronization systems built into commercial database software like Oracle make it possible to build huge database farms by linking together large numbers of synchronized servers. So far, leading open-source databases like PostgreSQL and MySQL provide only limited support for database synchronization. The open-source systems will probably catch up one day soon, but the technology is inherently difficult to develop.

Sometimes the information source being synched is a moving target. Consider Usenet, the original global bulletin board system. When two Usenet servers connect, they essentially synchronize their articles. If an article is on one machine but not the other, a copy is made to eliminate the discrepancy. Back in 1991, John Gilmore, one of the founders of the Electronic Frontier Foundation, said, “Usenet interprets censorship as damage and routes around it.” What he meant was this: any university or business that doesn’t like articles posted on Usenet may delete them from its server, but because the articles flow through the network as a whole, no one institution can block information from getting out to the world.

In recent years, Gilmore’s quotation has been reinterpreted by many journalists as referring to the Internet rather than Usenet. Sadly for both Gilmore and the cause of free speech, this alteration makes the quote inaccurate. When articles are published from a Web site, instead of through Usenet, they are indeed distributed from a central location-and that central location can be subject to censorship or other forms of political pressure.

Online file-swapping operations like Napster and Gnutella are really just very large synchronization services. Users have their own visions of what music or other files they want, and they sync and sync until they are happy. Here, “sync” applies not to an individual file but to a collection. The results, however, are much the same.

Downloading music from a file-sharing service is fundamentally different from downloading information over the Web. In the case of the Web, very few readers keep and redistribute their own long-term copies. This is why Napster and its descendants are threatening to the music industry; as Usenet showed, it can be exceedingly difficult to stop the spread of data through a large-scale synchronization system. Indeed, one of the great advantages of sync is redundancy: even if the “master” copy gets erased, sync invariably leaves many other copies around. This phenomenon makes it hard for outsiders to eradicate or control information that is shared by sync.

Understanding the uses and power of sync is vital for accurately predicting the direction that the Internet and e-commerce are likely to grow. Most people like the safety that comes from having data in multiple locations, and the speed that comes from having the data immediately available on their own computers. Products and services that offer sync, therefore, will probably fare better in the marketplace than similarly priced services that offer high-speed access to data stored on remote systems. People don’t want to just tap into a data stream; they want to have their own copy of the information, and they want it kept up-to-date. This has broad implications for everything from video on demand to home banking. I’ve been doing so-called Internet banking with Intuit’s Quicken software for years: every few days, I download my account’s most recent transactions and corrections over the Internet and add them to my register. My bank also lets me view my whole statement on the Internet. Would I give up downloading the transactions by themselves? Not on your life-I feel safer keeping my own copy.

Sync makes economic sense too. With sync, you aren’t so dependent on an expensive, always-on, high-speed Net connection. You can get much of the same effect with local storage and slow or even intermittent network connections. Sync really does mirror the way that the world has been built-as opposed to the way that pundits and engineers thought it would be.

In fact, even the Library of Alexandria was built through sync. Every ship that docked in Alexandria was searched for scrolls: if any were found, the ship was not allowed to leave until the scrolls were copied. Alas, the library’s hundreds of thousands of scrolls were lost when they were burned by Julius Caesar in 47 BCE because they didn’t sync a backup.

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