XML permits document authors to create markup (i.e., a text-based notation for describing data) for virtually any type of information. This enables document authors to create entirely new markup languages for describing any type of data, such as mathematical formulas, software-configuration instructions, chemical molecular structures, music, news, recipes and financial reports. XML describes data in a way that both human beings and computers can understand.
Figure 19.1 is a simple XML document that describes information for a baseball player. We focus on lines 5–11 to introduce basic XML syntax. You will learn about the other elements of this document in Section 19.3.