BINARY XML

Methods and apparatus, including computer program products, implementing techniques for encoding binary XML. The techniques include receiving data to be encoded and encoding the data as binary XML data. The binary XML data includes one or more elements. Each element is represented by an index number that identifies the element, a length number that indicates the length of the element's name, and token numbers that represent tags delimiting the element. The index numbers, length numbers, and token numbers are encoded as a sequence of bytes including at least one byte that represents a composite number. A composite number is a token number combined with either an index number or length number.