I/O Format: XML

The last important matter of business is to mention that all input and output for your command parser will be in XML (eXtensible Markup Language). If you've never heard of XML, ask your friend Google about it, and you'll be in no short supply of information, especially since the newest version of MS office replaces the .doc format with XML as the default. This is because XML offers a couple of major advantages to a standard text-based command parser; the first is that it is largely more relevant to a data structures course since the structure of XML is a general tree. The second is that XML is popping up all over the IT industry, and chances are that you will be dealing with XML at your place of employment. It's becoming the new standard for information exchange, so it's a good thing to be learning. Another great thing about XML is that, in the past, students were required to error-check the commands. Dr. Hugue is a dependability expert, and she believes strongly in writing dependable code; a malformed text command should not crash your program. XML is easily validated (both syntactically and structurally); so you can use pre-existing and readily available tools to confirm that both the input and output XML is error-free.

As of Java 5.0, Java contains many interfaces to process and validate XML. You are encouraged to take advantage of them. We will provide you with a Java class called XmlUtility which does most of the heavy lifting for you. It is discussed in another section.