On Tue, 17 Nov 2015 09:40:38 -0500, Denenberg, Ray <[log in to unmask]> wrote:

>Clearly there is confusion over "resource" - web resource, information 
resource, RDF resource. I'm not sure it's useful to sort through it all, as 
some of these definition have historical significance only.  So let's try to 
break this down without talking about resources. 

>An RDF property may be a datatype property or an object property. A 
datatype property takes a literal for its object (Quotes).  An object 
property takes an "individual" for its object (braces).   "Individual" as 
in, a member of an RDF class.  An individual always has an RDF description 
(or in your terminology, you can always make an RDF statement about it).

It's unclear to me where any of this comes from. It isn't an accurate 
description of RDF or RDFS, which have only one type of property 
(rdf:Property). OWL does have DatatypeProperty and ObjectProperty classes, 
but they are subclasses of rdf:Property; other types of properties are 
allowed.

Additionally, it is allowed, desirable, and common to link to resources on 
the web in Linked Data, even when they do not have RDF representations. 
Every item in DPLA, for instance has triples of the form:

  :aggregation a ore:Aggregation ;
     edm:isShownAt <http://example.com/some/item/page.html> .

  <http://example.com/some/item/page.html> a edm:WebResource .

Using a literal in place of that resource would be obfuscating and would 
prevent us and others from making additional assertions about it. Web pages, 
jpegs, ebooks, etc... *are* (or at least, can be) OWL individuals.

What you refer to as an "RDF resource" is only one of the kinds of things we 
want to talk about, and while it's good practice to have RDF descriptions, 
there are cases where this isn't feasible or necessary (e.g. because someone 
else controls the server that hosts the web page you want to describe).

I would also suggest using different terminology; as Karen has pointed out, 
"RDF resource" has a formal meaning within the specifications. A related 
concept that may interest you is "RDF source"[0], loosely: resources that 
provide an RDF Graph. This concept is used heavily in the recent Linked Data 
Platform spec[1].

[0] http://www.w3.org/TR/rdf11-concepts/#dfn-rdf-source
[1] http://www.w3.org/TR/ldp/#dfn-linked-data-platform-rdf-source


Tom Johnson
Metadata & Platform Architect
Digital Public Library of America