The domains of x, y, z and the components of time are specified by coordinates. The use of character sets other than ASCII is given by characters.
If external schemas are used, the names (and version numbers) of these schemas should be listed. Note that any time a user has classes additional to those defined as part of SAIF, the schema or schemas from which these classes come are considered as external and must be specified.
If additional classes have been used, then one of two situations may exist.
(1)The party receiving the data is aware of the schema(s) defining those classes and has no need to have the class definitions transmitted. If this is the situation, addedClasses is not specified.
(2)No prior understanding between the sender and receiver exists, and the addedClasses must be specified.