Example: XML
<title> Database Systems </title>
<author> <lastname> Date </lastname> </author>
<publisher> Addison-Wesley </publisher>
<title> Foundation for Object/Relational Databases </title>
<author> <lastname> Date </lastname> </author>
<author> <lastname> Darwen </lastname> </author>
<ISBN> <number> 01-23-456 </number > </ISBN>