Whether it be a major sporting event, the latest blockbuster movie, or a song that we have just purchased, we are obsessed with information about whatever it is we are watching or listening to: who was playing, who starred, who was the director, the artist, and so on. In fact, such information about something can often be as important as the thing itself.

Take, for instance, the photograph shown in Figure 5.3 of an oversize chick staring out indignantly from its mud-bowl nest, looking for all the world like a fluffy toy with its ludicrously big feet and bill. As an image it s cute of course, but when we discover that this chick will one day become a full-grown black-browed albatross a master of ocean flight with a wingspan of almost 8 feet (2.5 meters), the picture takes on a whole lot more meaning. Our interest is further enhanced when we learn that this photograph was taken on a small island in the South Atlantic one of the Falkland Islands at latitude 51 22' S and longitude 60 4' W, in the antipodean summer.

Figure 5.3: Image with associated metadata.

All of this information about a particular item of digital media is known in information technology circles as metadata.

When it comes to digital media, metadata is usually stored under a set of tags such as Title, Date, Description, and the like, as we can see in Figure 5.3. Some tags, such as Title, will be common to a...