Section 2.8 - Prolog and Document Type Declaration
The version number "1.0" should be used to indicate conformance to this version of this specification; it is an error for a document to use the value "1.0" if it does not conform to this version of this specification.
Section 5. - Conformance
5.1 Validating and Non-Validating Processors
5.2 Using XML Processors
Note that the final recommendation never mentions the word "parser", so the successful act of parsing an XML file for fatal and non-fatal errors is probably not sufficient.