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ditionally, XML files are operating system and application independent with the added benefit of mak- ing carriage-return/linefeed sequences almost a non-issue.

Unlike tab-delimited files, XML files explicitly state the meaning of each value in the file. Very little is left up to guesswork. Each element's value is explicitly described. XML turns data into information. The tab-delimited file from Figure 1.1 is simply an organized list of words and numbers. They have no con- text and therefore they only represent data. On the other hand, the words and numbers in XML files are given value and context, and therefore are transformed from data to information. Furthermore, it is very easy to create hierarchial data structures using XML. Figure 1.2 illustrates these concepts. Without very much examination, it becomes apparent the data represents a list of pets, specifically, six pets, and each pet has a name, age, type, and color. Was that as apparent in the previous example?

<pets> <pet> <name>Tilly</name> <age>14</age> <type>cat</type> <color>silver</color> </pet> <pet> <name>Amanda</name> <age>10</age> <type>dog</type> <color>brown</color> </pet> <pet> <name>Jack</name> <age>3</age> <type>cat</type> <color>black</color> </pet> <pet> <name>Blake</name> <age>12</age> <type>dog</type> <color>blue</color> </pet> <pet> <name>Loosey</name> <age>1</age> <type>cat</type> <color>brown</color> </pet> <pet> <name>Stop</name> <age>5</age> <type>pig</type> <color>brown</color> </pet> </pets>

As the world's production economies move more and more towards service economies, the stuff of busi- ness becomes more tied to data and information. Similarly, libraries are becoming less about books and more about the ideas and concepts manifested in the books. In both of these spheres of influence there needs to be a way to move data and information around efficiently and effectively. XML data shared between computers and computer programs via the hypertext transfer protocol represents an evolving method to facilitate this sharing, a method generically called Web Services.


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