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Re: subject/predicate/object terminology

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: Fri, 14 Feb 2003 20:57:36 +0000
Message-Id: <5.1.0.14.0.20030214205532.04e1af10@localhost>
To: Frank Manola <fmanola@mitre.org>, w3c-rdfcore-wg@w3.org

Well held that Man!  (English for "good catch")

The comment below on the vocab doc doesn't just apply to the reification 
section, there are many such instances, e.g.:

[[The triple

P rdfs:range C

states that P is an instance of the class rdf:Property, that C is an 
instance of the class rdfs:Class and that the resources denoted by the 
objects of triples whose predicate is P are instances of the class C.]

That one should go to comments.

Brian



At 12:02 14/02/2003 -0500, Frank Manola wrote:

>Following up on item 9 in today's agenda, here are some potential problem 
>areas in Concepts and Vocabulary (I don't claim these are exhaustive):
>
>Concepts Section 3.1 begins:
>
>"The underlying structure of any expression in RDF can be viewed as a 
>directed labelled graph, which consists of nodes and labelled directed 
>arcs that link pairs of nodes (these notions are defined more formally in 
>section 6). The RDF graph is a set of *triples*:
>
>[image of the RDF triple comprising (subject, predicate, object)]
>
>Each property arc represents a *statement* of a relationship between the 
>things denoted by the nodes that it links, having three parts:
>
>    1. a property that describes some relationship (also called a predicate),
>    2. a value that is the subject of the *statement*, and
>    3. a value that is the object of the *statement*.
>
>The direction of the arc is significant: it always points toward the 
>object of a *statement*.
>
>The meaning of an RDF graph is the conjunction (i.e. logical AND) of all 
>the *statements* that it contains."
>
>I've highlighted *triple* and *statement* in the above.  The text seems 
>mostly to be talking about the subject/predicate/object of *statements*, 
>except for the introduction, which seems to suggest it's talking about 
>*triples*.  A question is whether we're going to use subject, predicate, 
>and object for talking both about components of triples, and components of 
>statements and, if so, how we keep them straight.  Note that the abstract 
>syntax uses these terms to refer to parts of *triples*.
>
>Also, in bullets 2 and 3, tht term "value" is a bit ambiguous:  it could 
>be read either as referring to a URIref, or to the thing denoted by that 
>URIref.  Given the wording in the preceding phrase, changing "a value" to 
>"the thing" would clarify that it was talking about the thing denoted, 
>rather than the URIref (if that's what it is talking about).
>
>Concepts Section 3.4, the third sentence, says:
>
>"A literal may be the object of an RDF *statement*, but not the subject or 
>the arc"
>
>This seems to mix several things.  A literal sounds like the lexical 
>thing, which would be a reasonable object of a triple, but less-clear for 
>a statement (presumably it's the value denoted by the literal that would 
>be the object of a statement).  "Arc" seems to be mixing in the drawing 
>terminology from Section 3.1, and it's not clear it belongs here.
>
>Concepts Section 3.5 starts:
>
>"Some simple facts indicate a relationship between two objects. Such a 
>fact may be represented as an RDF triple in which the predicate names the 
>relationship, and the subject and object denote the two objects."
>
>In this section, the term "fact" is used as the thing represented as an 
>RDF triple.  In Section 3.1 the thing represented as a triple seemed to be 
>a "statement".  There may or may not be a problem using "fact" in this 
>kind of text, but its relationship to "statement" needs to be made 
>clear.  Also, "object" is used in two different ways, as the things 
>denoted by subjects and objects, and as the third component of a triple.
>
>Vocabulary Section 5.3.1:
>
>This section starts with some nice text that is clearly about subjects, 
>predicates, and objects of *statements*.
>
>Section 5.3.2 (rdf:subject) then says:
>
>"A *triple* of the form:
>
>S rdf:subject R
>
>states that S is an instance of rdf:Statement and that the subject of S is R"
>
>This may or may not be problematic.  The question is whether the reader 
>will interpret S and R as the URIrefs involved in the corresponding 
>triple, or as the resources denoted by S and R.  Similar comments apply to 
>sections 5.3.3 and 5.3.4.
>
>--Frank
>
>
>
>--
>Frank Manola                   The MITRE Corporation
>202 Burlington Road, MS A345   Bedford, MA 01730-1420
>mailto:fmanola@mitre.org       voice: 781-271-8147   FAX: 781-271-875
Received on Friday, 14 February 2003 15:56:26 EST

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