- From: Patrick Stickler <patrick.stickler@nokia.com>
- Date: Sun, 23 Jun 2002 15:03:02 +0300
- To: ext Brian McBride <bwm@hplb.hpl.hp.com>, RDF Core <w3c-rdfcore-wg@w3.org>
One additional suggestion: I think it's enough to restrict the inquiry to only tests C and D. The tests A and B are less illustrative of the core distinction between tidy and untidy interpretation of literals, and C and D will suffice to give users a clear picture of the distinction, enough (hopefully) to make a choice. Otherwise, folks could wonder why A can agree with either interpretation and may get confused about the distinction between A and B which is minor but makes B seem to be similar to A, etc. So I recommend that we remove A and B and re-label C and D as 1 and 2 (or T and U) and make the feedback a simple vote between the two (with optional comments). Cheers, Patrick On 2002-06-21 17:12, "ext Brian McBride" <bwm@hplb.hpl.hp.com> wrote: > > This is first draft of the datatypes message I agreed to produce at the f2f. > > Brian > ============================================================================= > > The RDFCore WG is producing a proposal for how XML Schema datatypes should > be used in RDF. We would like some guidance on a particular tradeoff we > have to make. > > The WG requests that you send your considered answers to > www-rdf-comment@w3.org, along with any comments, thoughts or questions you > may have. > > INTRODUCTION TO DATATYPES > ========================= > > Let's explain the basic ideas behind our approach to datatyping. We are > proposing two principal idioms for representing datatyped information. The > first looks like this: > > <Jenny> <age> _:a . > _:a <xsdr:decimal> "10" . > > This can be written in RDF/XML like this. > > <rdf:Description rdf:about="Jenny"> > <foo:age xsdr:decimal="10"/> > </rdf:Description> > > Here the b-node _:a denotes the integer 10 which can be represented in > decimal form as "10". The WG believes that this distinction between > numbers, e.g. 10 and numerals (which are strings) e.g. "10" is important if > we are to precisely define the semantics, e.g. 10 # "10". > > This idiom treats an XML datatype as a mapping from a value to a lexical > representation of the value; this mapping is represented in RDF by a property. > > We believe this idiom to be quite straightforward, but not sufficient on > its own because it is common practise to write things like: > > <jenny> <age> "10" . > > where the author of this fragment of RDF means to represent the fact that > Jenny's age is the number 10. This is the second idiom, which is where we > need some guidance. > > > SOME TEST CASES > =============== > > It is here that we need some advice, because we have a choice to make in > the way we define the formal semantics. > > A few simple test cases: > > Test A: > > <Jenny> <ageInYears> "10" . > <John> <ageInYears> "10" . > > Should an RDF processor conclude that the value of the ageInYears > properties for Jenny and John are the same? > > Test B: > > <Jenny> <ageInYears> "10" . > <Jenny> <testScore> "10" . > > Should an RDF processor conclude that the value of Jenny's ageInYears > property is the same as the value of Jenny's testScore property? > > Test C: > > <Jenny> <ageInYears> "10" . > <Film> <title> "10" . > > Should an RDF processor conclude that the value of Jenny's age property is > the same as the value of the Film's title property? If the value the > <ageInYears> property is an integer, and the value of the <title> property > is a string, they are not the same thing and are thus not equal. > > Test D: > > <Jenny> <ageInYears> "10" . > <ageInYears> <rdfs:range> <xsd:decimal> . > > <John> <ageInYears> _:a . > _:a <xsdr:decimal> "10" . > > Should an RDF processor conclude that Jenny and John have the same > age? [Note: in this example the range constraint is expressed using > rdfs:range. We may have to introduce a special datatyping range property, > but that is an independent detail for now.] > > It is not possible to have the answers to Test B, Test C and Test D all be > yes. Either B and C can be yes or D can be yes. We have to decide which > of these is the most important to have; (B and C) or D. > > WHY THESE TEST CASES MATTER > =========================== > > The formal semantics can define the meaning of a literal in one of two ways: > > tidy) the <ageInYears> property takes a value which is a numeral, i.e. a > string > > untidy) the <ageInYears> property takes a value which is some datatype > value whose string representation is "10", but without further > information, such as > a range constraint, we can't tell exactly what the value is, e.g. the > string might be in octal. > > If we choose the tidy option, the object of the statement is always a > string, which means that in: > > <Jenny> <ageInYears> "10" . > <Film> <title> "10" . > > the values of the two properties are the same; they are both the STRING "10". > > If we choose the untidy option, the value of the object object of the > statement is unknown from this statement alone; a range constraint is > required to determine the value from the literal string: > > <jenny> <ageInYears> "10" . > <ageInYears> <rdfs:range> <xsd:decimal> . > > With a range constraint, we can know that the object of the property is the > integer 10. > > CONCLUSION > ========== > > To end then, please send a message to www-rdf-comments@w3.org indicating > whether you believe its more important to have the answer to test case B be > yes, or test case D be yes: > > Test B: > > <Jenny> <ageInYears> "10" . > <Jenny> <testScore> "10" . > > Test D: > > <Jenny> <ageInYears> "10" . > <ageInYears> <rdfs:range> <xsd:decimal> . > > <John> <ageInYears> _:a . > _:a <xsdr:decimal> "10" . > > > We would also like to know the reasons for this preference. > > Brian McBride > on behalf of the RDFCore WG > > -- Patrick Stickler Phone: +358 50 483 9453 Senior Research Scientist Fax: +358 7180 35409 Nokia Research Center Email: patrick.stickler@nokia.com
Received on Sunday, 23 June 2002 07:58:37 UTC