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Re: subject/predicate/object terminology

From: Frank Manola <fmanola@mitre.org>
Date: Fri, 14 Feb 2003 16:23:12 -0500
Message-ID: <3E4D5E40.9000007@mitre.org>
To: Brian McBride <bwm@hplb.hpl.hp.com>
CC: w3c-rdfcore-wg@w3.org

I sure am glad I have editor's discretion on dealing with this stuff in 
the Primer.  If I didn't, I suspect we'd be looking at another Primer 
Last Call version sometime in July!


Brian McBride wrote:

> 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

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 16:07:45 UTC

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