Review Comment:
Temporal Representation and Reasoning in OWL 2
This paper presents a work on temporal knowledge representation and reasoning on the Semantic Web using OWL 2 and SWRL.
4D fluents and nary relations are presented in the first part as well as Allen relations.
SWRL inference rules are presented in the second part.
An evaluation is presented at the end of the paper.
This is available as a Protégé plugin.
This paper is interesting and well written, although some errors that must be corrected (see below). In particular there is a misunderstanding of W3C SW standards and of the status of other SW languages.
However, I wonder about the novelty and added-value of the paper because in my opinion, similar work already have been published in a way or another.
In addition, the evaluation part is not convincing at all (see below).
Details:
The real name is OWL 2 (not OWL 2.0)
"Formal definitions of concepts and of their properties form ontologies, which are defined using the OWL language"
->
RDFS or OWL languages
"existing Semantic Web standards (e.g., OWL, SWRL)"
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OWL is a standard, SWRL is not a standard
"Description Logics (DLs) are a family of Knowledge Representation languages that form the basis for the Semantic Web standards "
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No, the basis of SW standards are RDF, RDFS (i.e. labelled graphs) and SPARQL.
OWL is the standard for rich ontologies, on top of RDF/S.
"The OWL language is based on DLs and it is the basic component of the Semantic Web initiative."
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No, see above.
"triplets of the form object-predicate-subject"
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triples of the form subject-predicate-oject
"Classes of the object and the subject of a property are abbreviated as domain and range respectively. "
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Classes of the subject and the object of a property are abbreviated as domain and range respectively.
"adoption of OWL 2 as the current Semantic Web standard"
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adoption of OWL 2 as the current Semantic Web standard for rich ontologies
"Using an improved form of reification, the N-ary
relations approach [19] suggests representing an n-
ary relation as two properties each related with a new
object (rather than as the object of a property). "
->
Why two properties ? It is (at least) three : subject, object and time.
In Fig 2, using same properties for inverse properties is puzzling, you must argue for this.
"The N-ary relations approach referred to above is considered to be an alternative to the 4D-fluents approach considered into this work."
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ambiguous
"Building upon well established standards of the semantic web
(OWL 2.0, SWRL)"
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SWRL is not a standard
4D-fuents
->
4D-fluents
"CompanyName is static property"
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a static property
"each interval interval"
"sameAs OWL keyword"
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sameAs OWL property
"In our work, the temporal property remains a property relating the additional object with both the objects (e.g., an Employee and a Company) involved in a temporal relation."
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ambiguous
"Enforcing transitive properties is rather involved"
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What does that mean ?
"Specifically, when a property is temporal, if the domain of property is ClassA and the range is ClassB (where domains and ranges can be composite class definitions or atomic concepts), then using the N-ary representation the domain becomes ClassA OR Event and the range ClassB OR Event. Compared to 4D- fluents, the disjunction of concepts appearing both in domain and ranges of properties limits specificity of references of the N-ary representation."
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You can use two other properties for inverse and you would not have this problem.
Elaborate on reusing same properties for inverse.
"To the best of our knowledge, this is the only known solution to
this problem."
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Similar work has already been published, e.g. :
Time-Oriented Question Answering from Clinical Narratives Using Semantic-Web Techniques at ISWC 2010
"The maximal tractable subset of Allen relations containing all basic relations when applying path consistency comprises of 868 relations [18]. Tractable subsets of Allen relations containing 83 or 188 relations [30] can be used instead, "
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This notion of tractable subset containing 868 (or whatever) relations is not clear and should be explained.
"Since compositions and intersections are constant-time operations (i.e., a bounded number of table lookup operations at the corresponding composition tables) the running time of closure method is linear to the total number of relations of the identified tractable set. "
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This is not fair to talk about linear time as e.g. transitive closure might occur.
Page 11 says that OWL disallow transitivity and disjointness, hence SWRL must be used.
But page 12 says: "The required expressiveness of the proposed representation is within the limits of OWL 2 expressiveness."
In my opinion , there is a contradiction.
The evaluation part uses datasets of 10 to 100 individuals.
This is not realistic to have so few instances !
In addition, Table 3 shows that reasoning time with 100 individuals takes 11 seconds.
What about 1000, 10,000 or 100,000 individuals ?
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