How should the prose within the Z39.50 standard (in particular section 18.104.22.168.5) that discusses presentation contexts, be treated when there is no presentation layer?
Section 22.214.171.124.5 (Preferred-record-syntax) says:"The origin may specify a preferred record syntax for retrieval records. If the target cannot supply a particular record according to the Preferred-record-syntax, it supplies the record according to one of the other abstract syntaxes from the set for which Presentation contexts are currently established for this A-association.
If the target cannot supply the record according to either the requested syntax or a syntax corresponding to an established presentation context, it returns a surrogate diagnostic for that record, unless the established set of presentation contexts is empty; in that case, this standard does not prescribe the target action. "
When there is no presentation layer, it is assumed that " the established set of presentation contexts is empty". Therefore, if the target cannot supply the record according to the requested syntax, according to the prose cited above, "the standard does not prescribe target action".
Thus, since the text of Z39.50-1995 does not prescribe action in this case, a clarification has been developed to provide applicable guidelines: Server Selected Record Syntax