Writing XML documents is very straightforward, as I hope Chapters 3 and 4 proved. Reading XML documents is not nearly as simple. Fortunately, you don't have to do all the work yourself; you can use an XML parser to read the document for you. The XML parser exposes the contents of an XML document through an API, which a client application then reads. In addition to reading the document and providing the contents to the client application, the parser checks the document for well- formedness and ( optionally ) validity. If it finds an error, it informs the client application.