Thesis 65

The necessary standards for the representation and communication of structured data already exist.

From the perspective of someone unfamiliar with the details of contemporary information technologywhich is to say most of usone factor that might seem to stand in the way of everyware's broader diffusion is the wild heterogeneity of the systems involved. We've grown accustomed to the idea that an ATM card issued in Bangor might not always work in Bangkok, that a Bollywood film probably won't play on a DVD player bought in Burbankso how credible is any conception of the ubiquitous present that relies on the silky-smooth interplay of tag reader and wireless network, database and embedded microcontroller?

However intractable such issues may seem, their solution is in handif currently wedged somewhere in the gap between theory and robust praxis. Exactly how is a piece of information represented so that it may be reported by an RFID tag, put into proper perspective by visualization software, correlated with others in a database, and acted on by some remote process? How do such heterogeneous systems ever manage to pass data back and forth as anything more than a stripped-down, decontextualized series of values?

One of the first successful attempts to address such questions was the Standard Generalized Markup Language (SGML), adopted as the international standard ISO 8879 in 1986. SGML was intended to permit the sharing of machine-readable documents between different systems; its fundamental innovation, still observed in all the markup languages descended from it, was to propose that a document be provisioned with interpolated, semantic "tags" describing its various parts.^[*] For example, a document describing this book might mark it up (at least in part) like this:

^[*] Such tags are not to be confused with those of the RFID variety.

<title>Everyware</title>

<subtitle>The dawning age of ubiquitous computing</subtitle>

<author>Adam Greenfield</author>

<pubyear>2006</pubyear>

Once a document has been marked up this way, SGML-compliant but otherwise incompatible systems will parse it identically. Moreover, SGML is a metalanguage, a tool kit for the construction of interoperable special-purpose languages; as long as all observe the rules of valid SGML, any number of different applications can be built with it.

This would seem to make SGML the perfect lingua franca for technical systemsin theory, anyway. In practice, the language has some qualities that make it hard to use, most notably its complexity; it was also not ideally suited to the multilingual Internet, where documents might well be rendered in tightly-woven Farsi or the stolid ideograms of Traditional Chinese. In the late 1990s, therefore, a working group of the World Wide Web Consortium developed a streamlined subset of SGML known as XML (for eXtensible Markup Language) specifically designed for use in the Internet context.^[**]

^[**] Regrettably, the most recent version of XML still excludes support for several of the world's writing systems, notably the plump curls of Burmese and the hauntingly smokelike vertical drafts of Mongolian Uighur script.

While XML has the very useful quality that it is both machine-readable and (reasonably) legible to people, the source of its present interest to us is the success it has enjoyed in fostering machine-to-machine communication. Since its release in 1998, XML has becoming the lingua franca SGML never was, allowing the widest possible array of devices to share data in a manner comprehensible to all.

XML compatibility, inevitably, is not universal, nor has it been perfectly implemented everywhere it has been deployed. But it is a proven, powerful, general solution to the problem of moving structured data across systems of heterogeneous type and capability. Once again, we'll have to look elsewhere if we're interested in understanding why everyware is anything but a matter of the very near term.