- From: Andy Seaborne <andy@apache.org>
- Date: Wed, 7 Feb 2024 22:05:09 +0000
- To: RDF-star Working Group <public-rdf-star-wg@w3.org>
At the Friday subgroup meeting, the role of the blank node in option 2
was discussed. Part of that is how the blank node comes about.
Below attempts to describe the conversion of the Turtle syntax described
in the section "What we seem to agree on" in [1] for options 2 (Syntax+)
and option 3 (new RDF term) [2].
(The name of "rdf:nameOf" is not agreed but used for continuity with
seeking-consensus-2024-01.html)
[1]
https://lists.w3.org/Archives/Public/public-rdf-star-wg/2024Jan/0095.html
[2]
https://htmlpreview.github.io/?https://github.com/w3c/rdf-star-wg/blob/main/docs/seeking-consensus-2024-01.html
== Translation for options 2 and 3 (given name for occurrence)
The Turtle:
<< :e | :s :p :o >> :x :y .
In Option 2, the translation is:
:e rdf:nameOf _:blank .
_:blank rdf:subject :s .
_:blank rdf:predicate :p .
_:blank rdf:object :o .
:e :x :y .
In option 3, the translation is:
:e rdf:nameOf <<( :s :p :o )>>
:e :x :y .
where <<( :s :p :o )>> is an RDF term.
== Translation for options 2 and 3 (implicit named occurrence)
In Turtle:
<< :s :p :o >> :x :y .
In option 2, the translation is:
_:a rdf:nameOf _:blank .
_:blank rdf:subject :s .
_:blank rdf:predicate :p .
_:blank rdf:object :o .
_:a :x :y .
In option 3, the translation is:
_:a rdf:nameOf <<( :s :p :o )>>
_:a :x :y .
where <<( :s :p :o )>> is an RDF term.
== Case: Repeated text (given name)
<< :e | :s :p :o >> :x :y .
<< :e | :s :p :o >> :x :y .
-- Option2
Each use of << :e | :s :p :o >> generates a new set of triples.
Triples (NT-level)
## Fresh blank node per use:
:e rdf:nameOf _:blank1 .
_:blank1 rdf:subject :s .
_:blank1 rdf:predicate :p .
_:blank1 rdf:object :o .
:e rdf:nameOf _:blank2 .
_:blank2 rdf:subject :s .
_:blank2 rdf:predicate :p .
_:blank2 rdf:object :o .
:e :x :y . # One, because a graph does not have duplicates.
-- Option 3
Triples (NT-level)
## Two triples.
:e rdf:nameOf <<( :s :p :o )>>
:e :x :y .
<<( :s :p :o )>> is the same RDF term wherever it is used in a file.
== Case: Repeated text (implicit blank node)
<< :s :p :o >> :x :y .
<< :s :p :o >> :x :y .
-- Option2
Triples (NT-level)
## Fresh blank node per use:
_:a1 rdf:nameOf _:blank1 .
_:blank1 rdf:subject :s .
_:blank1 rdf:predicate :p .
_:blank1 rdf:object :o .
_:a1 :x :y.
_:a2 rdf:nameOf _:blank2 .
_:blank2 rdf:subject :s .
_:blank2 rdf:predicate :p .
_:blank2 rdf:object :o .
_:a2 :x :y.
-- Option 3
Triples (NT-level)
_:a1 rdf:nameOf <<( :s :p :o )>>
_:a1 :x :y .
_:a2 rdf:nameOf <<( :s :p :o )>>
_:a2 :x :y .
== Case: Turtle predicate-object lists
Comparing turtle syntax
## [A]
<< :e | :s :p :o >>
:x1 :y1 ;
:x2 :y2 .
and
## [B]
<< :e | :s :p :o >> :x1 :y1 .
<< :e | :s :p :o >> :x2 :y2 .
-- Option 2
## [A]
:e rdf:nameOf _:blank .
_:blank rdf:subject :s .
_:blank rdf:predicate :p .
_:blank rdf:object :o .
:e :x1 :y1 .
:e :x2 :y2 .
is different to
## [B]
:e rdf:nameOf _:blank1 .
_:blank1 rdf:subject :s .
_:blank1 rdf:predicate :p .
_:blank1 rdf:object :o .
:e rdf:nameOf _:blank2 .
_:blank2 rdf:subject :s .
_:blank2 rdf:predicate :p .
_:blank2 rdf:object :o .
:e :x1 :y1 .
:e :x2 :y2 .
Each use of << :e | :s :p :o >> cause a new blank node.
The generated blank nodes _:blank* make << | >> behave like [ ] in Turtle.
-- Option 3
<< :e | :s :p :o >>
:x1 :y1 ;
:x2 :y2 .
and
<< :e | :s :p :o >> :x1 :y1 .
<< :e | :s :p :o >> :x2 :y2 .
translate to the same triples.
## [A] and [B]
:e rdf:nameOf <<( :s :p :o )>>
:e :x1 :y1 .
:e :x2 :y2 .
The same rdf:nameOf triple, makes << | >> behave like URI terms.
== Case: Annotations 1
Annotations translate to named occurrences and these translate again to
the data model (here, written in N-Triples).
:s :p :o {| :x1 :y1 ; :x1a y1a |}
:s :p :o {| :x2 :y2 |}
which is (still in "agreed" syntax):
:s :p :o .
<< _:a1 | :s :p :o >> :x1 :y1 .
<< _:a2 | :s :p :o >> :x2 :y2 .
_:a1 :x1 :y1 .
_:a1 :x1a :y1 .
_:a2 :x2 :y2 .
for new blank nodes _:a1 and _:a2.
The :x1/:y1 and :x2/:y2 have been kept apart.
-- Option 2
Triples (NT level)
:s :p :o .
_:a1 rdf:nameOf _:blank1 .
_:blank1 rdf:subject :s .
_:blank1 rdf:predicate :p .
_:blank1 rdf:object :o .
_:a2 rdf:nameOf _:blank2 .
_:blank2 rdf:subject :s .
_:blank2 rdf:predicate :p .
_:blank2 rdf:object :o .
_:a1 :x1 :y1 .
_:a1 :x1a :y1a .
_:a2 :x2 :y2 .
-- Option 3
Triples (NT level)
:s :p :o .
_:a1 rdf:nameOf <<( :s :p :o >> .
_:a2 rdf:nameOf <<( :s :p :o >> .
_:a1 :x1 :y1 .
_:a1 :x1a :y1a .
_:a2 :x2 :y2 .
== Case: Annotations 2
:s :p :o {| :e | :x1 :y1 |}
:s :p :o {| :e | :x2 :y2 |}
translates to
:s :p :o .
<< :e | :s :p :o >> :x1 :y1 .
<< :e | :s :p :o >> :x2 :y2 .
:e :x1 :y1 .
:e :x2 :y2 .
-- Option 2
Triples (NT level)
:s :p :o .
:e rdf:nameOf _:blank1 .
_:blank1 rdf:subject :s .
_:blank1 rdf:predicate :p .
_:blank1 rdf:object :o .
:e rdf:nameOf _:blank2 .
_:blank2 rdf:subject :s .
_:blank2 rdf:predicate :p .
_:blank2 rdf:object :o .
:e :x1 :y1 .
:e :x2 :y2 .
-- Option 3
Triples (NT level)
:s :p :o .
:e rdf:nameOf <<( :s :p :o >> .
:e :x1 :y1 .
:e :x2 :y2 .
Received on Wednesday, 7 February 2024 22:05:19 UTC