5.2. The XML Information Set
The XML Recommendation does not specify the information that a parser should deliver. That has been rectified, at least in part, by the Infoset Recommendation, which states:
This specification defines an abstract data set called the XML Information Set (infoset). Its purpose is to provide a consistent set of definitions for use in other specifications that need to refer to the information in a well-formed XML document.
Conforming XML parsers are not required to implement exactly this information set, although, fortunately, many do so in one way or another. Some XML processors actually keep more detailed information about the data in an XML document than is officially in the XML infoset. Indeed, the Infoset Recommendation ...