An Object Type Definition (OTD) defines a MetaObject type, which (possibly used in combination with other types) forms the type of a particular Vobject. An OTD essentially contains documentation, expected linked objects, and protocol actions associated witha particular type.
An OTD is encoded with a special markup language, defined using XML This document can then be easily translated into text, HTML, XML-Schema, a database, or program code stubs, as well as parsed and interpreted by authoring tools, applications, etc.
For the formal OTD XML syntax, see the DTD at http://interreality.org/otd/otd.dtd.