W3C home > Mailing lists > Public > public-rdf-wg@w3.org > November 2012

review of RDF Concepts

From: Peter Patel-Schneider <pfpschneider@gmail.com>
Date: Wed, 28 Nov 2012 13:45:02 -0500
Message-ID: <CAMpDgVwPn8A34m53sFEk-qTREJNTGMMFaMKOqLmPOi2RoCAxLA@mail.gmail.com>
To: RDF WG <public-rdf-wg@w3.org>
I have a few changes to wording to correct what I see as errors.

Something needs to be done to fix the situation with respect to blank nodes,
but the issue note already warns about this so there is no need to hold up
publication right now.

I think that something needs to be done about social meaning.  I have
suggestions below.  As the sections involved at non-normative, I don't think
that publication needs to be held up until the problem is resolved.



Minor grammar changes:

0.1/ Be consistent with commas before "being".

0.2/ string, numbers -> strings, numbers

0.3/ "semantics" should be reserved for the model-theoretic semantics.  Use
"meaning" instead in other situations.

0.4/ "should" should be avoided except when it is "SHOULD".


Significant changes:

A/ I worry about Section 1.3 and the last bit of Section 6.  It appears to
me that this is edging back towards social meaning, which was ripped out of
RDF the last time around.

Initial suggestion for Section 1.3:

1.3 The Referent of an IRI

The resource denoted by an IRI is also called its referent. What exactly is
denoted by any given IRI is not defined by this specification.

Basic guidelines for determining the referent of an IRI are provided in
other documents, like Architecture of the World Wide Web, Volume One
[WEBARCH] and Cool URIs for the Semantic Web [COOLURIS]. A very brief,
informal and partial account of these guidelines follows:
- IRIs have global scope: An IRI is assumed to denote the same resource
  regardless of where the IRI occurs.
- By social convention, The IRI owner [WEBARCH] provides the
  can establish the intended referent by means of a
  specification or other document that explains what is denoted.
  <<RDF-SCHEMA is special here, FOAF would be a much better example>>
  For example, [RDF-SCHEMA] specifies the referents of various IRIs that
  start with http://www.w3.org/2000/01/rdf-schema#.
- A good way of providing the intended referent is to set
  up the IRI so that it dereferences [WEBARCH] to a document.  Such a
  document can, in fact, be an RDF document that describes the denoted
  resource by means of RDF statements.

Suggestion for the last bit of Section 6:

It is a good idea to, whereever reasonable, set up fragment identifiers in
RDF-bearing representations in a way that is consistent with
non-RDF representations. For example, if the fragment chapter1 identifies a
document section in an HTML representation of the primary resource, then the
IRI <#chapter1> should be taken to denote that same section in all
RDF-bearing representations of the same primary resource.


B/ Something needs to be done to Section 3.4.

There should be some wording here to indicate that blank nodes can be shared
between RDF graphs, but that simply reusing a blank node identifier between
to unrelated graphs results in different blank nodes.  There is more work
needed here as well.


Other changes:

1/ Change [required]:

This document defines an abstract syntax (a data model) which serves to link
all RDF-based languages and specifications, including:
- Serialization syntaxes for storing and exchanging RDF (e.g., Turtle
  [TURTLE-TR] and RDF/XML [RDF-SYNTAX-GRAMMAR]),
- the SPARQL Query Language [RDF-SPARQL-QUERY],
- the RDF Vocabulary Description Language [RDF-SCHEMA],
- a formal model-theoretic semantics for RDF [RDF-MT].

to:

This document defines an abstract syntax (a data model) for RDF.  Concepts
defined in this document are vital to understanding any aspect of RDF,
and support
- serialization syntaxes for storing and exchanging RDF (e.g., Turtle
  [TURTLE-TR] and RDF/XML [RDF-SYNTAX-GRAMMAR]),
- the RDF Vocabulary Description Language (RDFS) [RDF-SCHEMA],
- the formal model-theoretic semantics for RDF and RDFS [RDF-MT], and
- the SPARQL Query Language [RDF-SPARQL-QUERY].

*********************

2/ Change [strongly recommended]:

The core structure of the abstract syntax is a collection of triples, each
consisting of a subject, a predicate and an object. A set of such triples is
called an RDF graph. This can be illustrated by a node and directed-arc
diagram, in which each triple is represented as a node-arc-node link; hence
the term “graph”.

to:

The core structure of the abstract syntax for RDF is a set of triples, each
consisting of a subject, a predicate and an object. A set of such triples is
called an RDF graph. An RDF graph can be visualized as a node and
directed-arc diagram, in which each triple is represented as a node-arc-node
link.

*********************

3/ Change [picky wording change]:

There may be three kinds of nodes in an RDF graph: IRIs, literals, and blank
nodes.

to:

There can be three kinds of nodes in an RDF graph: IRIs, literals, and blank
nodes.

*********************

4/ Change [wording change]:

Any IRI and literal denotes

to:

Any IRI or literal denotes

*********************

5/ Change [very picky wording change]:

holds between the resources denoted by the subject and object.

to:

holds from the resource denoted by the subject to
the resource denoted by the object.

*********************

6/ Change [strongly recommended - there is no need to have referents to
define
a vocabulary]:

An RDF vocabulary is a collection of IRIs with clearly established referents
intended for use in RDF graphs.

to:

An RDF vocabulary is a collection of IRIs intended for use in RDF.

*********************

7/ Change [strongly recommended]:

An RDF dataset is a collection of RDF graphs. All but one are named graphs
associated with an IRI. The last one is the unnamed default graph, and is
often used to hold triples that involve the graph names.

A common use of RDF datasets is to hold snapshots of multiple RDF sources.

to:

An RDF dataset is a collection of RDF graphs.  All but one of these graphs
have an associated IRI.  These graphs are called named graphs, and the IRI
is called the name of the named graph.  The remaining graph does not have an
associated IRI.  It is called the default graph of the dataset.

There are many possible uses for RDF datasets.  One such use is to hold
snapshots of multiple RDF sources.   It is common to have the default graph
contain triples that involve the names of the other graphs in the dataset.

*********************

8/ Change [required - don't dump on the semantics]:

This
treatment of RDF graphs as logical expressions is normatively defined in the
RDF Semantics specification [RDF-MT], using the formalism of Model
Theory.

to:

The logical meaning of RDF graphs is normatively defined in the
RDF Semantics specification [RDF-MT], using a model-theoretic semantics.

*********************

9/ Change [grammar and clarification]:

An RDF graph A entail another RDF graph B if every possible arrangement of
things in the world that makes A true also makes B true. If the truth of A
is presumed or demonstrated, then the truth of B can be inferred.

to

An RDF graph A entails another RDF graph B if every possible arrangement of
the world that makes A true also makes B true. When A entails B, if the
truth of A is presumed or demonstrated then the truth of B is established.

*********************

10/ Change [grammar]:

A concrete RDF syntaxes

to:

Concrete RDF syntaxes

*********************

11/ Change [be cleaner about RDF meaning]:

semantics, which lies exclusively in the encoded graph or dataset.

to:

meaning, which is exclusively mediated by the encoded graph or dataset.

*********************

12/ Change [required, is currently false]:

This transformation does not change the meaning of an RDF graph, provided
that the Skolem IRIs do not occur anywhere else. It does however permit the
possibility of other graphs subsequently using the IRI to also refer to the
same entity, which was not possible when the node was blank.

to:

This transformation does not appreciably change the meaning of an RDF graph,
provided that the Skolem IRIs do not occur anywhere else. It does however
permit the possibility of other graphs subsequently using the Skolem IRIs,
which is not possible for blank nodes.

*********************

13/ Change [garden path grammar]:

An RDF Dataset is a collection of RDF graphs and comprises:

to:

An RDF Dataset is a collection of RDF graphs, and comprises:

*********************

14/ Change [grammar and false?]:

RDF re-uses the XML Schema built-in datatypes

to:

RDF uses many XML Schema datatypes



*********************

15/ Change [currently different from definition in RDF semantics]:

A datatype map is an implementation-defined set of <IRI, datatype> pairs
such that no IRI appears twice in the set and the IRI denotes the
datatype. It can be seen as a function from IRIs to datatypes.

to:

A datatype map is an implementation-defined set of <IRI, datatype> pairs
such that no IRI appears twice in the set. It can be seen as a function from
IRIs to datatypes.


*********************

16/ Change [false]:

Otherwise, the literal is ill-typed, and no literal value can be associated
with the literal. Such a case, while in error, is not syntactically
ill-formed.

to:

Otherwise, the literal is ill-typed, and no literal value can be associated
with the literal. Ill-typed literals are not syntactically ill-formed and,
while
ill-typed literals are not normal, just their use does not make an RDF graph
inconsistent.
Received on Wednesday, 28 November 2012 18:45:30 GMT

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