[Definition: The key words must, must not, required, shall, shall not, should, should not, recommended, may, and optional in this specification are to be interpreted as described in [IETF RFC 2119].]
[Definition: The term information set refers to the output of an [XML 1.0] or [XML 1.1] processor, expressed as a collection of information items and properties as defined by the [XML Information Set] specification.] In this document the term infoset is used as a synonym for information set.
[Definition: The term fatal error refers to the presence of factors that prevent normal processing from continuing.] [Definition: The term resource error refers to a failure of an attempt to fetch a resource from a URL.] XInclude processors must stop processing when encountering errors other than resource errors, which must be handled as described in 4.4 Fallback Behavior.