Carroll2005named question 1 by lebo
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CSCI 6966 Advanced Semantic Web (Fall 2008)
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A Question from Tim Lebo about carroll2005named:
When comparing TriX to RDF/XML, the authors state, "The URI at which an RDF/XML document is published is used for three different purposes: as a retrieval address, with an operational semantics; as a means of identifying the document; and as a means of identifying the graph described by the document. There is potential for confusion between these three uses." The URIRef for a named graph performs only the latter function (identifying the graph).
- When encountering a URIref in a set of triples (e.g., ":G1 pr:disallowedUsage pr:Marketing ." in section 5.3), how does a crawler know that the URIRef identifies a named graph?
- When a crawler determines that a URIRef names a named graph (e.g., 'ng') , how does it obtain the rdfgraph(ng)? Would the process require anything different from the proposed methods for obtaining descriptions for a "plain old" rdfs:Resource?
Jesse Weaver Presents Named Graphs
- Answer: Good questions. ONE: I believe the answer is not explicit in the article, but it seems to be implied. Consider the quote from section 8.1: "We will consider two such intentions expressed by the properties swp:assertedBy and swp:quotedBy. These take a named graph as a subject ...." Then, note in Fig. 1 that the subject of swp:assertedBy is labeled as an rdfg:Graph. From these two pieces of information, it seems that a named graph can be identified as being rdf:type rdfg:Graph. More formally, for a named graph ng, ng is in the class extension of rdfg:Graph (ICEXT(I(rdfg:Graph))). Thus, if a URIref u is countered, and it is the subject of a triple u rdf:type rdfg:Graph, then the crawler knows it's a named graph. TWO: I believe the assumption is that the crawling will occur over a set of named graphs and that the crawler will somehow have knowledge of how to obtain rdfgraph(ng) from name(ng). Consider first that in named graphs, all graphs have a name (i.e., there is no "default graph" like in SPARQL). Therefore, if a crawler is already crawling a graph, that means it already had some way of obtaining it. In whatever way the crawler obtained that graph, it would obtain other graphs. The last paragraph of section 3.5 seems to indicate that method of retrieval is independent of the named graphs approach. What is important is that a name is associated with each graph and that there exists a way to obtain the graph (and such a way is not specified in the article).
Facts about Carroll2005named question 1 by leboRDF feed
| A | Question + |
| About | Carroll2005named + |
| Author | Tim Lebo + |
| Question answer | Good questions. ONE: I believe the answer … Good questions. ONE: I believe the answer is not explicit in the article, but it seems to be implied. Consider the quote from section 8.1: "We will consider two such intentions expressed by the properties swp:assertedBy and swp:quotedBy. These take a named graph as a subject ...." Then, note in Fig. 1 that the subject of swp:assertedBy is labeled as an rdfg:Graph. From these two pieces of information, it seems that a named graph can be identified as being rdf:type rdfg:Graph. More formally, for a named graph ng, ng is in the class extension of rdfg:Graph (ICEXT(I(rdfg:Graph))). Thus, if a URIref u is countered, and it is the subject of a triple u rdf:type rdfg:Graph, then the crawler knows it's a named graph. TWO: I believe the assumption is that the crawling will occur over a set of named graphs and that the crawler will somehow have knowledge of how to obtain rdfgraph(ng) from name(ng). Consider first that in named graphs, all graphs have a name (i.e., there is no "default graph" like in SPARQL). Therefore, if a crawler is already crawling a graph, that means it already had some way of obtaining it. In whatever way the crawler obtained that graph, it would obtain other graphs. The last paragraph of section 3.5 seems to indicate that method of retrieval is independent of the named graphs approach. What is important is that a name is associated with each graph and that there exists a way to obtain the graph (and such a way is not specified in the article). ch a way is not specified in the article). |
| Question asked | When comparing TriX to RDF/XML, the author … When comparing TriX to RDF/XML, the authors state, "The URI at which an RDF/XML document is published is used for three different purposes: as a retrieval address, with an operational semantics; as a means of identifying the document; and as a means of identifying the graph described by the document. There is potential for confusion between these three uses." The URIRef for a named graph performs only the latter function (identifying the graph).
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| Question asked by | Tim Lebo + |
| Question for the Presentation | Jesse Weaver Presents Named Graphs + |
| Text | When comparing TriX to RDF/XML, the author … When comparing TriX to RDF/XML, the authors state, "The URI at which an RDF/XML document is published is used for three different purposes: as a retrieval address, with an operational semantics; as a means of identifying the document; and as a means of identifying the graph described by the document. There is potential for confusion between these three uses." The URIRef for a named graph performs only the latter function (identifying the graph).
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