The purpose of this Technical Specification is to define the syntax rules for a data stream for the submission of printing data to a Hybrid Mail operator or between Hybrid Mail operators. The Technical Specification defines a XML Schema Definition (XSD) describing the data stream. The description is based upon the XML (eXtended Mark-up Language) definition of rules and semantics for defining an XSD. The purpose of this is to offer a generalised syntax description that can provide seamless integration with a number of existing applications generating data that is liable to be forwarded to or from a Hybrid Mail operator. The use of an XSD will ensure that the documents confirm to the standard defined and that the output has the correct syntax. Software manufacturers can use an XSD to program applications that will produce ¿correct¿ outputs. This Technical Specification defines the syntax for creating a data stream that will eventually be converted into a deliverable. The overall object (a batch) can be divided into one or more objects that again can be divided into objects. The hierarchy includes bundles that contains a common part and letters. Each object has a number of characteristics attached to it. This diagram shows the structure of a HML (Hybrid Mail Language) document: each letter is self-contained (contains all the necessary information to be delivered on a certain destination).