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RDF Syntax - simplified Non XML RELAXNG

From: Jonathan Borden <jonathan@openhealth.org>
Date: Thu, 7 Mar 2002 15:53:17 -0500
Message-ID: <054301c1c61a$1e01ac40$0a2e249b@nemc.org>
To: <www-rdf-comments@w3.org>
In my endevours to develop a good XML representation for KIF and N3, I have
been playing around with extending the RDF syntax. This has highlighted a
few points regarding the RDF syntax.

1) Consider representing bNodes (in NT) as NCNames i.e. no-colon names. RDF
otherwise disallows non namespace qualified elements and attributes. The RDF
syntax might use non namespace qualified elements and attributes to
represent bNodes.

2) Consider eliminating rdf:_n entirely from the _XML syntax_, that is a
parser can convert rdf:li to rdf:_2 or whatever. It is not possible to
create a proper formal grammar for RDF using commonly available tools and
languages if rdf:_n is allowed i.e. it is not possible to constrain "n" to
be an integer using any well known XML schema language.

It is not readily apparent from reading the Syntax WD how the syntax of
containers is intended to map onto NTriples. Although this can be deduced
from the test cases, it would be helpful to describe this in prose, as it is
a change from RDF 1.

3) prohibit use of unknown names in the RDF namespace.

4) A simple and easy to include addition to the syntax is to allow nested
rdf:RDF elements i.e. as the object of a statement. The contents of a nested
rdf:RDF might be interpreted as a collection of reified statements or as an
"N3 context" whose set of statements might be interpreted by the MT as
"unasserted". In any case it is a simple addition to the syntax.

Included is a compacted RDF syntax expressed as a non-XML RELAXNG grammar.
This grammar is also available at: http://www.openhealth.org/RDF/RDFs.rngnx

You see that it is quite compact.

[[
# RELAXNG non-XML grammar for RDFs - simplified RDF grammar
# Jonathan Borden 3/7/2002
namespace local = ""
namespace rdf = "http://www.w3.org/1999/02/22-rdf-syntax-ns#"
datatypes xsd = "http://www.w3.org/2001/XMLSchema-datatypes"

start = RDF

# rdf:RDF ? allow rdf:ID
RDF = element rdf:RDF{rdf:ID?,desc*}
# perhaps unqualified names refer to bNodes
# var =   element local:*{empty} | attribute local:*{""}
# an rdf:Description or typedNode
desc =   subject{predobj*}
subject =  element (* - (local:*,rdf:*)) |
    rdf:Description |
    rdf:Alt|rdf:Seq|rdf:Bag
   {
    (attribute rdf:about{anyURI}|
     attribute rdf:ID{xsd:NMTOKEN})?,
     attribute rdf:bagID(xsd:NMTOKEN)?,
     attribute rdf:type{anyURI}?
   }
predicate = (element * - (rdf:*,local:*)) | element rdf:li | element
rdf:value
predobj =  predicate{
    attribute rdf:ID{xsd:NMTOKEN}?,
    attribute rdf:bagID{xsd:NMTOKEN}?,
    obj |
    attribute rdf:resource{anyURI} |
    (attribute rdf:parseType{"Resource"},obj+) |
    (attribute rdf:parseType{text - "Resource"}, any)
    } |
   predAttr
predAttr =  attribute * - (local:*,rdf:*)| attribute rdf:value {text}
# this is extended to allow rdf:RDF (i.e. context/bundle) as the object of a
statement
obj =   subject |
   text |
   RDF
any =  mixed { element * { attribute * { text }*, any }* }
]]

Jonathan
Received on Thursday, 7 March 2002 15:55:56 GMT

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