GTW Time in RDF

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Presentation given at CSCI 6966 Advanced Semantic Web (Fall 2008)#Lesson 11

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Presentation slides

• Speaker: Gregory Todd Williams
• Title: Introducing Time into RDF
• Authors: Claudio Gutierrez, Carlos A. Hurtado, and Alejandro Vaisman
• Conference: IEEE Transactions on Knowledge and Data Engineering, vol. 19(2): 207-218
• URL: http://www2.computer.org/portal/web/csdl/doi/10.1109/TKDE.2007.34
• Date of Presentation: 2008/11/13

Questions

ID	Question	Name	Answer
GTW Time in RDF Jesse Weaver	Section 1.1.3 essentially describes the vocabulary for temporal labeling as RDF reification with temporal information hanging off the equivalent of an rdf:Statement. Could this potentially introduce unexpected results? For example, if :subj1 owl:sameAs :subj2, then by inference, all of the temporal information attached to triples with subject :subj1 would also be attached to triples with subject :subj2. This is a problem for the traditional usage of reification (providing metainformation about triples), but is it a problem for this case? It seems reasonable that if :s :p :o is true for a time frame, and :s owl:sameAs :s2, then :s2 :p :o would also be true for the same time frame. What do you think? Do you foresee any such issues with this approach?	Jesse Weaver
Gutierrez2007introducing question 1 by lebo	How does the work presented in this paper differ from OWL Time? Could OWL Time be used to extend the temporal labels used by Gutierrez et al.?	Tim Lebo
Gutierrez2007introducing question 2 by lebo	According to Footnote 3, the authors "chose not to ((use the standard reification vocabulary of RDF)) to stress the fact that the notions presented in this paper are independent of any view one may have about the concept of reification in RDF." Yet the "temporal label" is constructed in the exact same way the standard reification vocabulary would do it (:tsubj rdfs:subPropertyOf rdf:subject . :tpred rdfs:subPropertyOf rdf:predicate . :tobj rdfs:subPropertyOf rdf:object.). How can the authors reproduce the standard reification approach while pretending to stay at arms length from the standard?	Tim Lebo
Time into rdf ankesh	In section 3.2 authors simply mention 'we present the semantics for the notion of entailment for temporal graphs based on the corresponding notion of RDF graphs'. Later they use the notion of entailment in RDF graphs to prove Theorems 3 and later. I believe that it would have been convenient for readers if authors had included a line for RDF entailment (and-or a reference), like G1 entails G2 if an instance of G2 is subclass of cl(G1). What do you think? Have I missed something that authors have said in the paper? I was expecting more from this paper. My feeling is that even with timestamping their work is scoped to snapshot. The temporally reified statements are used to group them into graphs with same time-stamps for all purposes (entailment), except for probably querying. They leave incorporation of <, >, = comparisons for future work. I was looking for entailments such (a, b, c){1,5} entails (a, b, c){4}, by inclusion of some axiomatic triples or other means. There is another thing that may merit attention- transitivity of intervals. For example, (a,b,c){1,3}, (a,b,c){3,5} entails (a,b,c){1,5}.	Ankesh Khandelwal

Attendees

Tim Lebo