message to RDF entailment implementors

One thing that I think would be nice to send out to implementers of RDF
entailment systems is something saying what has changed.   Here is a draft
of the information.  Comments are welcome.

peter


  Entailment-visible changes for RDF 1.1 (informative)

Most of the changes between RDF and RDF 1.1 do not have any effect on
implementations of entailment, but there are a few minor changes.

The sequence in which the versions of entailment are defined has changed.
Datatype entailment is now defined on top of simple entailment, and then
RDF and RDFS entailment are defined on top of datatype entailment.  RDF
entailment has two required datatypes xsd:string and rdf:langString, but
this doesn't appreciably add to RDF entailment as these two datatypes
replace plain literals.

Plain literals are divided into xsd:string literals for plain literals
without language tags and rdf:langString literals for plain literals with
language tags.  There is thus no need for an implementation to have
separate data structures for plain literals and datatyped literals,
although rdf:langString is a special datatype as it has a language tag in
addition to a lexical form and thus requires special treatment.  The zero
Unicode character is not allowed in xsd:string, but was allowed in plain
literals, so there is a minor change here.  Implementations that have a
special internal data structure for plain literals might not need to
otherwise change.

One change that does affect entailment is that invalid literals (e.g.,
"a"^^xsd:integer) are immediately inconsistent for recognized datatypes.

There is a list of XML Schema datatypes that are deemed suitable for use
within RDF.  They are all optional except for xsd:string.

The rdf:XMLLiteral datatype is now optional.  rdf:HTML is a new optional
datatype; implementation experience and illustrative tests are requested.
rdf:PlainLiteral is a newish optional datatype; implementation experience
and illustrative tests are requested.