Foreword


In 1976, two landers named Viking set down on Mars and turned their dish-shaped antennae toward earth. A few hours later, delighted scientists and engineers received the first pictures from the surface of another planet. Over the next few years , the Viking mission continued to collect thousands of images, instrument readings , and engineering data ”enough to keep researchers busy for decades and making it one of the most successful science projects in history.

Of critical importance were the results of experiments designed to detect signs of life in the Martian soil. At the time, most researchers considered the readings conclusive evidence against the prospect of living organisms on Mars. A few, however, held that the readings could be interpreted in a more positive light. In the late 1990's, when researchers claimed to have found tiny fossils in a piece of Martian rock from Antarctica, they felt it was time to revisit the Viking experiment and asked NASA to republish the results.

NASA staff retrieved the microfilm from storage and found it to be largely intact and readable. They then began scanning the data, intending to publish it on CD-ROM. This seemed like a simple task at first ”all they had to do was sort out the desired experiment data from the other information sent back from the space probes. But therein lay the problem: how could they extract specific pieces from a huge stream of munged information? All of the telemetry from the landers came in a single stream and was stored the same way. The soil sampling readings were a tiny fraction of information among countless megabytes of diagnostics, engineering data, and other stuff. It was like finding the proverbial needle in a haystack.

To comb through all this data and extract the particular information of interest would have been immensely expensive and time-consuming . It would require detailed knowledge of the probe's data communication specifications which were buried in documents that were tucked away in storage or perhaps only lived in the heads of a few engineers, long since retired . Someone might have to write software to split the mess into parallel streams of data from different instruments. All the information was there. It was just nearly useless without a lot of work to decipher it.

Luckily, none of this ever had to happen. Someone with a good deal of practical sense got in touch with the principal investigator of the soil sampling experiment. He happened to have a yellowing copy of the computer printout with analysis and digested results, ready for researchers to use. NASA only had to scan this information in and republish it as it was, without the dreaded interpretation of aging microfilm.

This story demonstrates that data is only as good as the way it's packaged. Information is a valuable asset, but its value depends on its longevity, flexibility, and accessibility. Can you get to your data easily? Is it clearly labeled? Can you repackage it in any form you need? Can you provide it to others without a hassle? These are the questions that the Extensible Markup Language (XML) was designed to answer.



Learning XML
Learning XML, Second Edition
ISBN: 0596004206
EAN: 2147483647
Year: 2003
Pages: 139
Authors: Erik T. Ray

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