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@ Emw: Hi, rdf:type is not reflexive, as if it where, we would have doggy_the_dog rdf:type doggy_the_dog ... did I miss something ? subclass of is though, as every class is a subclass of itself. TomT0m ( talk) 16:50, 18 April 2015 (UTC)
R
is a relation in which for all element x
of the domain of the relation, xRx
. If a relation is not reflexive, it implies that for some element x there is not(xRx). So rdfs:Class type rdfs:Class can totally hold if not. Did I miss something in the rdfs:Class definition ?
TomT0m (
talk) 17:18, 18 April 2015 (UTC)
I, just so we can talk and try to avoid misunderstanding : RDFS is included into RDF, see /info/en/?search=Resource_Description_Framework#RDF_vocabulary and the primer of the W3C: the primer notes RDFS spec as a part of the RDF spec. So there is no point into claiming this is an extension. THis may be true historically but it is now included in RDF. Would you agree ? TomT0m ( talk) Another document to prove my point : http://www.omgwiki.org/odmftf/lib/exe/fetch.php?id=archive%3Aftf1&cache=cache&media=10_rdfs_metamodel_rev.pdf TomT0m ( talk) — Preceding undated comment added 17:37, 18 April 2015 (UTC)
I don't understand how rdfs helps to capture type/token distinction better than rdf alone, because everything that is only the subject of a rdf:type statement can be considered a token, and on the right of rdf:type of a type.
In rdfs however, even a metaclass is an instance of class. So it is a type in a sense, but a higher order type, not a plain type with tokens instances. TomT0m ( talk) 16:58, 18 April 2015 (UTC)
@ Emw: Re. thinking about it I think it is a bad idea to focus in the introduction to OWL and RDF are they are just one of the many ontology languages, and the metaclass concept may apply to all of them. I'd rather cite them as a (significant) example, and focus on how useful metaclasses are with mapping real world concepts such as species, more technically on their application as pattern of classes (example : they map very well to definition like a chemical element is a type of atom defined by the same atomic number, where the atomic number is defined in the metaclass instanciation, and third by their use in modelling of languages itself, to contextualize the mention that RDFS is its own metamodel. All of these are real application of Metaclasses. Then we focus in the body of the article. TomT0m ( talk) 10:06, 20 April 2015 (UTC)
@ Chocolateboy: Can you be more specific ? TomT0m ( talk) 11:14, 11 May 2015 (UTC)
The first sentence is currently: "In the Semantic Web, a metaclass is a class whose instances are classes."
And 'class' is never linked to another article which expands on what a class is.
On metaclass, the first sentence is currently: "In object-oriented programming, a metaclass is a class whose instances are classes."
Is a class in the Semantic Web the same as a class in computer programming? If not, what is it? John Vandenberg ( chat) 01:35, 23 July 2015 (UTC)
The article implicitly suggests two different definitions of metaclasses.
The (A) quantification is supported in the article's introduction as well as in the
RDF and RDFS subsection.
It is stated that metaclasses [can] be easily created by using rdf:type in a chain-like fashion
,
i.e. the two RDF triples A rdf:type B
and B rdf:type C
ensure that C
is a metaclass.
The (B) quantification is supported in the recently added
Metaclass classification section
through a reference to a paper by D. Foxvog
[1]. (According to the paper's page 2,
metaclasses are classes each of whose instances is necessarily a class
.)
Moreover, the
article does not provide any references which would support the (A) case. On the other hand, several references exist (they can be found in the literature) that support the (B) case: in addition to
[1], there is
Stefik & Bobrow
[2],
Magkanaraki et al.
[3],
and
Koide & Takeda
[4]
[5].
In
[3], metaclasses are delimited as exactly the subclasses of the rdfs:Class
(the authors make a claim that classes of classes should not be considered metaclasses unless they are descendants of rdfs:Class
).
In
[4] all metaclasses must hold
. In
[5], the class rdfs:Class
as superclassUnitOfMeasure
from the SUMO ontology is given as an example of an ill-structured metaclass
that should be remedied
by making it a subclass of owl:Class
.
See
What Is a Metaclass? for details.
Hundblue (
talk) 17:28, 30 March 2016 (UTC)
The delimitation of metaclasses as subclasses of a built-in metaclass can also be observed in the paper about Protégé-2000
[6]
that is cited in the
Protégé subsection:
all metaclasses inherit from the system class
(page 10).
Hundblue (
talk) 19:57, 30 March 2016 (UTC)
:CLASS
{{
cite web}}
: Explicit use of et al. in: |author=
(
help)
{{
cite conference}}
: CS1 maint: multiple names: authors list (
link)
This article has not yet been rated on Wikipedia's content assessment scale. |
This article links to one or more target anchors that no longer exist.
Please help fix the broken anchors. You can remove this template after fixing the problems. |
Reporting errors |
@ Emw: Hi, rdf:type is not reflexive, as if it where, we would have doggy_the_dog rdf:type doggy_the_dog ... did I miss something ? subclass of is though, as every class is a subclass of itself. TomT0m ( talk) 16:50, 18 April 2015 (UTC)
R
is a relation in which for all element x
of the domain of the relation, xRx
. If a relation is not reflexive, it implies that for some element x there is not(xRx). So rdfs:Class type rdfs:Class can totally hold if not. Did I miss something in the rdfs:Class definition ?
TomT0m (
talk) 17:18, 18 April 2015 (UTC)
I, just so we can talk and try to avoid misunderstanding : RDFS is included into RDF, see /info/en/?search=Resource_Description_Framework#RDF_vocabulary and the primer of the W3C: the primer notes RDFS spec as a part of the RDF spec. So there is no point into claiming this is an extension. THis may be true historically but it is now included in RDF. Would you agree ? TomT0m ( talk) Another document to prove my point : http://www.omgwiki.org/odmftf/lib/exe/fetch.php?id=archive%3Aftf1&cache=cache&media=10_rdfs_metamodel_rev.pdf TomT0m ( talk) — Preceding undated comment added 17:37, 18 April 2015 (UTC)
I don't understand how rdfs helps to capture type/token distinction better than rdf alone, because everything that is only the subject of a rdf:type statement can be considered a token, and on the right of rdf:type of a type.
In rdfs however, even a metaclass is an instance of class. So it is a type in a sense, but a higher order type, not a plain type with tokens instances. TomT0m ( talk) 16:58, 18 April 2015 (UTC)
@ Emw: Re. thinking about it I think it is a bad idea to focus in the introduction to OWL and RDF are they are just one of the many ontology languages, and the metaclass concept may apply to all of them. I'd rather cite them as a (significant) example, and focus on how useful metaclasses are with mapping real world concepts such as species, more technically on their application as pattern of classes (example : they map very well to definition like a chemical element is a type of atom defined by the same atomic number, where the atomic number is defined in the metaclass instanciation, and third by their use in modelling of languages itself, to contextualize the mention that RDFS is its own metamodel. All of these are real application of Metaclasses. Then we focus in the body of the article. TomT0m ( talk) 10:06, 20 April 2015 (UTC)
@ Chocolateboy: Can you be more specific ? TomT0m ( talk) 11:14, 11 May 2015 (UTC)
The first sentence is currently: "In the Semantic Web, a metaclass is a class whose instances are classes."
And 'class' is never linked to another article which expands on what a class is.
On metaclass, the first sentence is currently: "In object-oriented programming, a metaclass is a class whose instances are classes."
Is a class in the Semantic Web the same as a class in computer programming? If not, what is it? John Vandenberg ( chat) 01:35, 23 July 2015 (UTC)
The article implicitly suggests two different definitions of metaclasses.
The (A) quantification is supported in the article's introduction as well as in the
RDF and RDFS subsection.
It is stated that metaclasses [can] be easily created by using rdf:type in a chain-like fashion
,
i.e. the two RDF triples A rdf:type B
and B rdf:type C
ensure that C
is a metaclass.
The (B) quantification is supported in the recently added
Metaclass classification section
through a reference to a paper by D. Foxvog
[1]. (According to the paper's page 2,
metaclasses are classes each of whose instances is necessarily a class
.)
Moreover, the
article does not provide any references which would support the (A) case. On the other hand, several references exist (they can be found in the literature) that support the (B) case: in addition to
[1], there is
Stefik & Bobrow
[2],
Magkanaraki et al.
[3],
and
Koide & Takeda
[4]
[5].
In
[3], metaclasses are delimited as exactly the subclasses of the rdfs:Class
(the authors make a claim that classes of classes should not be considered metaclasses unless they are descendants of rdfs:Class
).
In
[4] all metaclasses must hold
. In
[5], the class rdfs:Class
as superclassUnitOfMeasure
from the SUMO ontology is given as an example of an ill-structured metaclass
that should be remedied
by making it a subclass of owl:Class
.
See
What Is a Metaclass? for details.
Hundblue (
talk) 17:28, 30 March 2016 (UTC)
The delimitation of metaclasses as subclasses of a built-in metaclass can also be observed in the paper about Protégé-2000
[6]
that is cited in the
Protégé subsection:
all metaclasses inherit from the system class
(page 10).
Hundblue (
talk) 19:57, 30 March 2016 (UTC)
:CLASS
{{
cite web}}
: Explicit use of et al. in: |author=
(
help)
{{
cite conference}}
: CS1 maint: multiple names: authors list (
link)