XML
XML is a standard for data storage, data representation and transmission that can allow multiple data producers, data consumers and applications to communicate with each other using the data without knowing about the intricacies of each other. XML documents can be self-describing using XML DTD or XML Schema, so applications need not know the data format in advance. An understanding of XML will allow programmers to represent their data in XML as well as understand existing data in XML format. XML is the mother of many other languages including HTML!
