- From: Jeremy Carroll <jjc@hpl.hp.com>
- Date: Thu, 02 Aug 2007 20:43:39 +0100
- To: Garret Wilson <garret@globalmentor.com>
- CC: Story Henry <henry.story@bblfish.net>, Sandro Hawke <sandro@w3.org>, Lee Feigenbaum <lee@thefigtrees.net>, Richard Cyganiak <richard@cyganiak.de>, Tim Berners-Lee <timbl@w3.org>, Semantic Web <semantic-web@w3.org>
Garret Wilson wrote: > The name of the president and whether it is unique is a red herring. The > main question is whether a US president could be a literal in the RDF > abstract syntax. The answer is yes; use the president's social security > number or some other identifying number, if names confuse the issue: > "123-45-6789"^^eg:uspresident. Correct. However, your datatype eg:uspresident is unlikely to be widely supported so this would be a poor engineering decision. > > In fact, any resource could be an instance of rdfs:Literal in the RDF > abstract syntax, if you decide to give it an identifying string. Those > same resource would not be literals if you used URIs to identify them > rather than strings. Having a concept of rdfs:Literal bring no > additional value to the RDF abstract syntax. Again correct - but to represent an arbitrary resource one would need a user defined datatype, and a private agreement between implementors as to its lexical-to-value mapping. > > Another way of summarizing things: the string "10" only relates to the > value 10 in the context of datatype xsd:integer (which is a subclass of > xsd:decimal). The string "10" would relate to the value 2 in the context > of the datatype eg:binary. The string "10" doesn't relate to any number > by itself---only in the context of some datatype. Correct > That means you cannot > talk about an RDF integer literal using only the string "10"; > you must > use "10"^^<|http://www.w3.org/2001/XMLSchema#integer>. Correct in the abstract syntax, but then that is intended for maximum clarity, and not intended for usability. A better surface syntax would allow you to simply write 10. You are free to design such a surface syntax. > > Some people are telling me that there is some huge, unbridgeable divide > between the following two representations: > > |"10"^^<|http://www.w3.org/2001/XMLSchema#integer>| > <|http://www.w3.org/2001/XMLSchema#integer:|10|>| > > They look pretty similar to me, except that the latter allows me to > treat so-called "literals" just like any other resource. No, incorrect. In the RDF Semantics some other resource e.g. http://example.org/10 has an unknown denotation, whereas "10"^^<|http://www.w3.org/2001/XMLSchema#integer> has a known denotation, the number 10. If you wanted to modify RDF so that http://www.w3.org/2001/XMLSchema#integer:|10| denoted the number 10, then that would be a fairly large change, in that it would be necessary to specify which URIs did datatype magic, and which do not. Jeremy -- Hewlett-Packard Limited registered Office: Cain Road, Bracknell, Berks RG12 1HN Registered No: 690597 England
Received on Thursday, 2 August 2007 19:44:02 UTC