To further illustrate the concept of structure, imagine a stack of printed paper invoices. If you want to merely store
these invoices as images for future retrieval and display, you can scan them and save them in a graphic format. On the
other hand, if you want to derive information such as monthly totals and average sales, such graphic storage would not
be useful. Instead, you could store the invoice data in a (structured) spreadsheet format so that you can perform the
requisite computations. Actually, most data you encounter are best classified as semistructured. Semistructured data
have already been processed to some extent. For example, if you look at a typical Web page, the data are presented
in a prearranged format to convey some information. The database types mentioned thus far focus on the storage and
management of highly structured data. However, corporations are not limited to the use of structured data. They also
use semistructured and unstructured data. Just think of the valuable information that can be found on company e-mails,
memos, and documents such as procedures, rules, and Web pages. Unstructured and semistructured data storage and
management needs are being addressed through a new generation of databases known as XML databases. Extensible
Markup Language (XML) is a special language used to represent and manipulate data elements in a textual format.
An XML database supports the storage and management of semistructured XML data.