- From: Patrick Stickler <patrick.stickler@nokia.com>
- Date: Mon, 5 Apr 2004 12:01:20 +0300
- To: "ext Rob Shearer" <Rob.Shearer@networkinference.com>
- Cc: <public-rdf-dawg@w3.org>, "ext Janne Saarela" <janne.saarela@profium.com>
On Apr 03, 2004, at 04:08, ext Rob Shearer wrote: > > The problem of datatype support has been addressed as part of the OWL > effort. Specifically, formal semantics of how reasoners should behave > when presented with datatypes they do not support have been specified. > This of course leads to the question of whether a DAWG conformant knowledge store is an OWL reasoner, and thus, to what extent the OWL specs have anything to say about DAWG conformant behavior. But I think we should certainly reuse anything/everthing we can from OWL and other relevant specs. > I think this came up as part of OWL because it was the first time > anybody had specified formal semantics for doing just about anything > with regards to the meaning of RDF or XML beyond verifying its lexical > representation. An RDF query language which allows datatype predicates > would be the second. It makes a lot of sense not to set a precedent of > reinventing these semantics for every semantic processor of XML schema > datatypes. > > The existing semantics > (http://www.daml.org/2002/06/webont/owl-ref-proposed#DatatypeSupport) > are: > > As a minimum, tools must support datatype reasoning for the XML Schema > datatypes xsd:string and xsd:integer. I would expect support as well for xsd:dateTime at the very least, for a DAWG conformant solution. The other proposed datatypes, while having merit, are not as critical insofar as most of the use cases I've seen. > For unsupported datatypes, > lexically identical literals should be considered equal, whereas > lexically different literals would not be known to be either equal or > unequal. Unrecognized datatypes should be treated in the same way as > unsupported datatypes. Right. Patrick > >> -----Original Message----- >> From: Patrick Stickler [mailto:patrick.stickler@nokia.com] >> Sent: 02 April 2004 00:21 >> To: ext Janne Saarela >> Cc: public-rdf-dawg@w3.org >> Subject: Re: PS-8: Query with Datatype Value Comparison & >> Support for Arbitrary Datatypes in Query >> >> >> >> >> On Apr 02, 2004, at 10:49, ext Janne Saarela wrote: >> >>> >>> >>> Following yesterday's teleconference I would like to continue >>> discussion on this support for arbitrary datatypes in a query. >>> >>> I suggested that if the support is really for any arbitrary >>> datatype, for a DAWG recommendation compatible RDF query >>> processor we need to lay a set of minimal datatypes it needs >>> to support. This would enable us to lay a minimal set of >>> operators that operate on these datatypes. >>> >>> I suggest the minimal set of datatypes would be a >>> subset of all XML Schema datatypes. I leave it up to >>> further discussion to see which ones are truly necessary. >> >> I support both of these requirements. >> >> 1. Any typed literal value which can be expressed in RDF/XML must >> also be expressible in the DAWG QL in terms of the same datatype >> URI and lexical form. There are thus no restrictions on the >> datatypes that one can use to express a query. >> >> If a given datatype expressed in a query is not recognized/supported, >> the query either fails, since no comparisions can be made, or (my >> preference) a warning/error is issued about the unsupported datatype). >> >> 2. A core set of datatypes, ideally based on the XML Schema predefined >> datatypes, will be specified as manditory. >> >> As for the latter, the list should be as short as possibly. Perhaps >> only: >> >> xsd:string >> xsd:decimal, and some/all its derived subtypes >> xsd:date >> xsd:dateTime >> xsd:anyURI >> xsd:base64Binary >> xsd:boolean >> >> >> Patrick >> >> >> >>> >>> Janne >>> >>>> A client wishes to discover all resources which are of rdf:type >>>> ex:Person, and have an ex:ageInYears which is between >> "16"^^ex:count >>>> and "18"^^ex:count, inclusive. >>>> The client is aware of a knowledge source from which such >>>> resources might be discovered. >>>> Following the DAWG recommendation, the client formulates a query >>>> which expresses the desired characteristics to match and submits >>>> the query to the knowledge source. >>>> The knowledge source returns zero or more resource descriptions >>>> describing the matched resources. >>>> -- >>>> I deliberately used unknown datatypes in this example to illustrate >>>> the need to be able to allow arbitrary datatypes in input queries, >>>> regardless of what datatypes a particular query resolution engine >>>> may be able to handle. >>>> Note that if the client is able to include auxiliary knowledge >>>> which may be relevant to resolution of the query along with >>>> the query itself (e.g. in a single input RDF graph) this >> would allow >>>> the client to provide information about the terminology used >>>> in the query, such as about the nature of particular datatypes, >>>> their relationship to other datatypes, and even references to >>>> formal definitions of the datatypes which could be used by the >>>> knowledge source to evaluate typed literals and perform >> comparisons. >>>> E.g. the auxiliary knowledge could indicate an XML Schema which >>>> defines the datatype in question, and if the knowledge source is >>>> able to understand XML Schemas, could load and utilize to deal >>>> with values of that datatype. >>>> -- >>>> Patrick Stickler >>>> Nokia, Finland >>>> patrick.stickler@nokia.com >>> >>> >>> -- >>> Janne Saarela <janne.saarela at profium.com> >>> Profium, Lars Sonckin kaari 12, 02600 Espoo, Finland >>> >>> >> >> -- >> >> Patrick Stickler >> Nokia, Finland >> patrick.stickler@nokia.com >> >> > > -- Patrick Stickler Nokia, Finland patrick.stickler@nokia.com
Received on Monday, 5 April 2004 05:02:41 UTC