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Re: RDF Interpretation of XML documents (was Re: [xml-d

• To: clbullar@i... ("Bullard, Claude L (Len)")
• Subject: Re: RDF Interpretation of XML documents (was Re: [xml-d
• From: John Cowan <jcowan@r...>
• Date: Tue, 20 Aug 2002 14:12:39 -0400 (EDT)
• Cc: jcowan@r... ('John Cowan'), vdv@d..., xml-dev@l..., rexb@s...
• In-reply-to: <2C61CCE8A870D211A523080009B94E430752B82F@HQ5> from "Bullard, Claude L (Len)" at Aug 20, 2002 12:47:14 PM

"Bullard, Claude L (Len)" scripsit:

> I like that.   That makes it worth some extra effort.

Me too.

> Just curious... how can the RDF processor do that; 
> does it assume an XML parse and then work from that 
> essentially as any namespace-aware processor could?

Yes.  An RDF processor is layered on an XML processor (a SAX parser, e.g.)
and extracts facts of the form "Resource S has property V with value O"
from the result of XML parsing, where:

	S can be URI-labeled or anonymous;
	V is URI-labeled;
	O can be:

		a URI-labeled resource,
		an anonymous resource,
		a string, or
		arbitrary XML.

Canonical RDF is contained in an rdf:RDF container, but this is not required
if the processor has some other way of deciding what to work on.

The interpretation algorithm is as follows:

1) Let the level of an element be its nesting depth, where level 1 represents
immediate children of the rdf:RDF element (or implicit equivalent).

2) Odd-level elements represent resources; even-level elements represent
properties.  The GI of a resource element is the resource's type; the
GI of a property element is the property name.  (RDF names are created by
concatenating the localname to the namespace name.

3) The value of a property element is:
	if it's empty and has an rdf:resource attribute, the resource specified
		by the URI in the attribute value;
	if it has character content, the string which is the character content;
	if it has a child element, the anonymous resource represented by
		the child element;
	if it has any other content, the content as literal XML.  (In this
		case there must be an attribute rdf:parseType with value
		"literal" for full RDF compliance.)

4) Attributes on a resource element are minimized string-valued properties
of the resource.  Attributes on a property element are minimized string-valued
properties of an anonymous resource which is the value of the property.

RDF has three built-in types with special syntax that represent bags,
sequences, and sets of alternates.  See RDF Model & Syntax for details.
Untyped resources can be designated using resource elements with a GI
of rdf:Description.

-- 
John Cowan          http://www.ccil.org/~cowan        jcowan@r...
To say that Bilbo's breath was taken away is no description at all.  There are
no words left to express his staggerment, since Men changed the language that
they learned of elves in the days when all the world was wonderful. --The Hobbit

• References:
  • RE: RDF Interpretation of XML documents (was Re: [xml-d
    • From: "Bullard, Claude L (Len)" <clbullar@i...>

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